My final report: After testing eight different mice, I became quite enamored with the multi-button functionality of the Logitech G502 for office productivity work. Plus, as a gaming mouse, it has a great sensor. I also like the light click forces of the L and R buttons. My only complaints are that it's a bit flatter in front than the MS mouse (making clicking the L and R buttons more fatiguing when using a fingertip grip) and, while lighter than many other mice, still weighs 30% more than the Intellimouse (it falls in the middle among the eight I tried). The attached photo shows how I programmed it for use with OS X. [ "Left Screen" and "Right Screen" mean resize the active window so that it takes up exactly half the screen, and put in on the left or right side, respectively. Very useful when you wish to have two windows displayed side-by-side.]
I also really liked the G502's scroll wheel -- it's unlike any mouse scroll wheel I've ever used before, and the best I've ever tried. It's metal, and has a nice weight to it, so when you switch it to free-spinning mode and flick it, it can fly up and down a long document extremely quickly. And in click mode it gives excellent control, with a really nice tactile feel. [Some don't like the metal, preferring a rubberized scroll wheel surface; I might prefer that as well, but the metal doesn't bother me; it's deeply notched to give good grip.] In addition, I really like that one can push the scroll wheel left or right in addition to down; I've programmed left and right to back and forward, respectively, which is great for surfing the web. [At least for me personally, flicking the scroll wheel back and forth is easier than hitting programmable side buttons on the mouse; this is an advantage of the G502 over, for instance, the G602 -- i.e., the G602 has the same number of programmable buttons, but doesn't have L and R functionality in the scroll wheel.]
I found Logitech's OS X-specific gaming software fully-compatible with 10.10.5, since it has allowed me to adjust the DPI and program all 11 buttons. Even the surface tuning works. Note: Based on a suggestion I read elsewhere, I store the profiles on the computer rather than the mouse ("Automatic Game Detection" rather than "On-Board Memory"); I've been told this works better with a Mac (On-Board Memory may work just as well, but I've not tried it).
MICE I TRIED; ALL ARE WIRED EXCEPT AS SPECIFIED. WEIGHTS DON'T INCLUDE THE WIRE:
MICROSOFT INTELLMOUSE OPTICAL (BASELINE), 91 g
LOGITECH G602 (SEE ABOVE), 121 g.
LOGITECH MX MASTER (WIRELESS), 145 g: I tried the MX Master in the store and didn't really like it -- it's fairly heavy, and doesn't have better functionality than a standard five-button mouse (same 5 programmable buttons, except one of the side buttons is so small as to be unusable; compensating for this, it has a side scroll wheel; call it a wash). If you want a wireless mouse of that size and shape, I'd instead recommend the Logitech G602.
LOGITECH G602 (WIRELESS), 130 g w/ one AA battery (153 g with two): The G602 is a good mouse, with the same number of programmable buttons as the G502 (11); and it works fine with just one battery, which leaves it 14 grams lighter than the MX Master (yes, you can feel the difference). And it does have a better slope on the L/R buttons than the 502 (at least for me). OTOH, they require more click force.
Overall, though, I prefer the 502 to the 602. I found the other buttons on the G502 more comfortable and easier to access. I also preferred the G502's scroll wheel. Another issue with 602 is that its transmitter needs to be plugged directly into the computer to avoid losing contact with the mouse, which I can't do (I need to plug it into a USB hub), since my computer only has two USB ports, and one goes to my hub, while the other goes to my backup hard drive (which also has to be plugged in directly to the computer). This is not a deal-breaker for me, it just means you need to program a shortcut into your keyboard for a macro that quits and restarts the Logitech software as needed (about once every day or two). I believe this would also be an issue with the MX Master. Finally, the G502's a bit lighter. [Also, the feet started coming off the G600, but I doubt that's a general problem -- likely just an issue with the particular unit I had.]
LOGITECH G600, 133 g: I'll add (to my previous post) that, after more time with the G600, I decided it just wasn't comfortable for me, because (in addition to the issues mentioned earlier), there is no good place to rest my thumb (basically, I need to rest it on top of the button panel, which isn't comfortable for me -- there's no stable resting place, so my thumb is never relaxed). Also, even though it weighs about the same as the G602 (with one battery), it feels decidedly heavier (maybe because of the cord, maybe because I can't grab it as well, or maybe because its slide pads aren't as good). I also had software issues with it that I didn't experience with the other LG mice, involving spontaneous profile switching. IIRC it has an on-the-fly profile switching option (which the other LG mice lack); and while I never used that (at least knowingly), I found it would sometimes switch to a new profile on its own. I suppose I could have figured out how to fix that, but I never put in the effort. My point is that the G600 offers a complication I didn't need.
LOGITECH M500, 121 g: I tried the 5-button Logitech M500 because it looked like it might be a nice shape, was light, and was quite inexpensive. However, by comparison with these other higher-end mice, the scroll wheel and click action felt nowhere near as nice, and (in spite of its light weight) felt a bit heavy (maybe it has lower-quality feet than the other mice). Plus, as mentioned above, I was strongly gravitating towards the additional functionality of the G602.
RAZER DEATH ADDER CHROMA, 105 g: Nice mouse, lightweight, good tracking. Also liked the very low forces required to click the L and R buttons. But its shape didn't suit me -- too wide and flat. Also, it didn't have the multi-button functionality of the G502. And, while Razer's software works with OS X, it's not well-designed -- I had to do some tricky stuff (with help from Razer tech support) to reprogram the buttons. [With Logitech, by contrast, this was straightforward.]
STEELSERIES SENSEI RAW (90 g) AND KANA (82 g): These are closest to the MS mouse in shape and weight, though not quite as comfortable (and they require a bit too much force to click). Their main problem is that I couldn't get the SteelSeries software to work, even though it was (and still is) listed on their website (Steelseries.com/Downloads) as compatible with OS X 10.7 and later. [In particular, Engine 2 (required for the Kana) couldn't recognize it; and Engine 3, required for theSensei, kept crashing.] After wasting a lot of time going back and forth by email with SteelSeries' QA, I was told that neither of these is currently compatible with 10.10 (indeed, according to SteelSeries, Engine 3 doesn't even work with 10.9 -- so this is not the case of a company getting caught off-guard by a recent OS update breaking their software). Needless to say, I didn't appreciate wasting all that time because SteelSeries knowingly puts false information on their site. I complained about this to them but, not surprisingly, the misinformation is still there (see second pic).