I've generally found that all my network compatability problems in Linux have been configuration or hardware related (I've had a couple of dodgy network cards die on me recently which caused some problems).
Once I have everything set up properly and working I've had less trouble hooking my Windows and Linux boxes together than I just randomly get with two Windows boxes, and it seems to be noticably faster to transfer files, especially lots of small ones.
As far as the UI goes I know what your talking about. For me I'm happy to use the CLI and even prefer it sometimes since I have to learn a lot of the command s for work anyway, and it helps to use a CLI remotely since it's much faster. This issue is one that the Ubuntu team seem to be concentrating on pretty closely so with any luck the next couple of versions of Ubuntu should make some strides on this one.
You could probably speed up your startup by dumping some stuff your not using, get rid of CUPs if your not doing any printing, drop Apache if you don't need a web server. There are probably a lot of things that are starting up that you don't use... That's not to say finding them and making sure you don't need them won't be a bit of an effort, but it's all a learning experience...
If I didn't have to edit IBM templates which contain some of the worst use of tables I have ever seen in a word document then I probably wouldn't ever use MS office again... And I always thought that Outlook was a complete POS, well before I had thunderbird to save me from having to look at it. But I guess the world has room for differing opinions. I do miss having Zoom-player on my media box since I moved it to kubuntu but mplayer and vlc work just fine for me and the ability to do just about everything in mplayer with the keyboard should make eventually setting up my remote control a lot easier.
There are a lot of games distributed with K/Ubuntu, but most of them are either pretty old or puzzle/card type games. That said there are still a few games like UT2K4 and Quake3 that have been released with native Linux installers. Aditionally the Cedega project is making fairly impressive strides towards windows compatability for games and many windows games, even fairly recent ones, will run on Linux just fine.
In the end even if the above help you I doubt they'll change your mind but it's definately worth keeping an eye on the Ubuntu distros. I fully expect some of your issues to be resolved by the next major release...
