No Finder takes second place, super buggy and freezey and crashy.
On your computer perhaps. I've personally extremely rarely had Finder crash on me with any version of OSX, for that matter and when it did it was usually a 3rd party bug with XtraFinder or something that the author usually fixes pretty fast. The fact that after a decade they haven't added a dual-pane option, though while adding just plain STUPID "features" to OSX does boggle the mind, though, but XtraFinder fixes most of these problems very well. They should just license/buy the code from him.
Frankly, I think a list of annoying problems introduced in recent OSX releases (possibly including Mountain Lion or not since I can't check now) isn't a bad idea. I've included a few from various other sources, but most are my own observations:
1> Mail still buggered as the thread title acknowledges
2> You can't open Windows or PPC ISOs with Disk Utility, Disk Image Mounter or Toast Titanium any longer. I had to download The Unarchiver just to open the contents (still don't "Mount"). This one is pretty annoying for some people looking to add virtual CD/DVDs to WINE as mentioned in another thread by someone. It just doesn't make sense to add more Microsoft compatible networking features like SMB2 and Exchange to OSX, but then ditch the ability to read Windows ISO images.... One has to wonder if they simply overlooked something in their race to make everything Cocoa and 64-bit and it just got short-changed or something.
3> You can't preview many formats with Quickview (spacebar in Finder) any longer due to Quicktime X (which isn't related to Quicktime 9 in the same way that Final Cut X isn't related to Final Cut 9) not supporting them or the old plugins for Quicktime 9. This is even more annoying than not being able to open ISOs since this comes up often if you have any number of .AVI or .MKV type videos in your media library. But just as annoying, iTunes/AppleTV never supported these formats either so if you have them, too darn bad, I guess. You either convert, run XBMC or some other program or buy a Windows machine that isn't so damn limited.
4> If you have check for automatic updates, the update "reminder" has no dismiss/quit/never option. You either tell it to BUG YOU tomorrow or do it right then or turn off checking for automatic updates.... ANNOYING AS HELL.
5> 3rd party non Apple signed software not only has to be checked to even work in preferences ala the new annoying as hell "Gatekeeper", but the Firewall settings will IGNORE the program on EVERY SINGLE RUN despite settings in the Firewall for it. In other words, if I run XBMC 12.3 here, it will ask me every single time I run it if I want to allow XBMC to take incoming connections and point me to the Firewall settings to make it go away. The problem is it's already in the Firewall settings as "allowed" and deleting it and manually entering it makes no difference. Since it's not an Apple developer signed App, Apple JUST IGNORES THEIR OWN FIREWALL SETTING FOR IT. This is INCREDIBLY ANNOYING and Mavericks makes it much more difficult to change the flag for it to stop doing that. The point is that it SHOULD respect YOUR decision in the Firewall settings for ANY app and not pester you with some stupid requester every fracking time you run it. This one is UNFORGIVABLE IMO and Apple has not done anything about it long before even Gatekeeper came into being (i.e. Firewall has been buggered on and off in different ways since I dunno...Leopard? The fact is they have (or at least had) two separate firewalls that don't talk well to each other and one is SHELL only). It just works? BS. It hasn't worked right in a long time, although I thought it was working OK until recently, but then I didn't have to update XBMC until recently, so I may have not noticed as I probably flagged the older version to not do that which isn't as simple anymore in Mavericks.
6> 10.9.0 had a dock that could migrate from monitor to monitor, but only if it was on the bottom. As far as I can tell here in 10.9.1, it won't migrate to another monitor in any position now. WTF can't they just have a dock on each monitor like they have for the menu bar now? It's just unreal the stupidity at Apple that they can't think of something so darn basic.
7> Apple's power saving sleep settings IGNORE NFS network connections to your machine so if you use your computer as a server to other devices (e.g. XBMC boxes) and use NFS, you can't let your computer sleep or it will go to sleep in the middle of watching a video, etc. as it only recognizes SMB and AFP as reasons to not let the computer sleep even though they ship OSX with NFS also (and don't support it in "sharing" either even though it seems to be more reliable than either one for working across multiple OS/systems).
8> FaceTime doesn't like many 3rd party webcams. I have a Logitech model with full OSX support and stereo mics and full 720P Skype support and 1080p recording support (forget model offhand as I'm not at home) and it works great in Skype, but in Facetime, sooner or later the image "stutters" on a single frozen frame with an alternating animated frame creating a "Max Headroom" like effect until I lower it to the dock and back or move into the exact same position as the frozen frame where it magically unfreezes. Only the Logitech camera does this (i.e. my built-in webcam on my MBP does not, but my Mini doesn't have a webcam so I bought the Logitech). It's pretty annoying, but I won't hold my breath on Apple fixing a problem with someone else's camera even though they leave Mini users few options (the Logitech blows away Apple's cameras, though and has stereo sound even and works perfectly in Skype and other apps).
Those are the ones I can think of off the top of my head. Feel free to add others as long as they're problems in general and not just one on your particular machine. I've reported several of these issues to Apple, but I think they just toss most feedback right into the trash can, to be honest.