Vista has been stable, and reliable for me.
1. Obnoxious unresizable dialog windows that make it annoying to read text.
2. Search feature is grossly inaccurate. I use grep for searching file contents, and 'dir /s' for finding files, both of which work perfectly.
3. File extension program associations needs work. In the file explorer right click context menu 'open with' option dialog, it doesn't recognize SeaMonkey to open .txt files when selected as the program to do so. It just ignores me. Also in the 'open with' dialog, an older version of CodeBlocks is on the commonly used program list for opening files and when I select the new version of CodeBlocks as the program to use, it ignores me.
4. Automatic updates isn't as smart as it thinks it is. I automatically disable this and run Windows Update manually because it recommends drivers that are either out of date, or not recommended for use with the laptop. If I had it enabled, who knows whether it would download the out of date drivers and install them or not.
5. Windows Genuine Advantage Validation blah blah annoying hoops to jump through. WGAV is necessary to download most Microsoft software, and I had to update it once :
The Windows Genuine Advantage validation program 'genuine.exe' fails with Error code : 0x80040266
(Code not available. The validation code could not be obtained...)
I had to use Internet Explorer , download an ActiveX control , and the information bar that lets you install the control doesn't show up until several minutes after the page is done loading. So in reality the page is still loading even though it doesn't tell you that and so I ended up doing it about 5 times before it worked.
6. More Explorer.exe problems :
a. Folder view states are often forgotten even when the setting to keep them is explicitly on.
b. There are some kind of implicit folder "types" that have their own settings like for music files / image files / whatever else they built into Explorer, and I can't just set a default view for all the folders on the disk to 'details' and sort by 'type', but I have to set it for each invisible folder "type", and I keep discovering more types of folders than I care for.
c. Forced auto scroll in the folder view pane of explorer that always scrolls exactly when I don't want it to, which is basically all the time.
7. The audio stack in Vista has changed for the worse from XP to Vista. In XP, all the available channels and their level settings were easily available. In Vista, the channel only shows up when you actually use it, and some settings are obscured / not easily found for working with a microphone and sound input.
So, other than all that, after you learn to avoid the "features" and annoyances that Vista has, it's a fairly good operating system. Like I said, it's main operation has been stable and reliable for me.
Don't get me started on the junky integrated SigmaTel audio though. Avoid it at all costs.
Oh yeah, Vista or XP? I say go for Vista. It's overall look is nicer than XP's plainness window wise. I still like XP alot though.
One last gripe about Vista though, the Control Panel takes forever to open up from the start menu, and the madness with the My* folders has got to go.