Most syncingest phone...now...
So, a year changes and what to do?
I think SE and Cingular have a little mutual contract going whereby Cingular gets all the latest SE phones first (of note, the z500 and the s710), which is why TMobile is no longer carrying any.
I am in the process of upgrading from a z600, which really fit the bill for the topic of this thread, perfectly, to a Nokia 6630. We'll see how that goes - I know that there will not be iSync support until 10.4, but I should be able to make do with Phone Agent until then. Worst comes to worst, I'll get a s710 from SE when I can get an unlocked one.
Y'all might want to check out the z800 as a possible good choice if you are big into SE, or else the s700/s710 are great choices if you don't mind paying a premium. Otherwise, Nokia is releasing some awesome phones at the moment, as is Samsung (surprisingly!). Check out
My World Phone.com for some killer deals on the latest and greatest - all unlocked for your personal provider.
As for Cingular and net access...they aren't the cheapest, but for GSM offerings, they have got the fastest system in place for data, using 3G/EDGE. Very cool - I can watch tv on my phone, streaming ;-)
So far I have been happy with Cingular. Don't waste a dime on the RAZR - I'd sell it if someone gave it to me. Also, I've heard the bluetooth amplifier has issues and will often times have a very limited range. Plus, build quality sucks. SE's still have the best build quality out there. The only thing going for Moto's at the moment is the hype and the fact that many of their phones are quad-band, so you can truly roam around. FYI - Cingular uses the 850Mhz spectrum, where as T-Mobile uses the 900Mhz spectrum, so keep that in mind when choosing phones.
Good luck - I'll run down the 6630 and my syncing experiences when I have a better idea...