Windows Vista has a lot
going for it that most people don't really hear about. It's
understandable because marketing some of these new features would
essentially be tantamount to saying "Oops, XP had some problems". 

What makes Windows Vista a much better experience aren't due mainly
to the  major new features. Instead,  it's the hundreds of barely
documented improvements to the OS that users notice but quickly take
for granted -- at least until they have to go back to using Windows XP
for awhile.  The big features like a new security layer, integrated
search, game & DVD exploring, DirectX 10, backup, Aero, kernel
overhaul, better audio handling, Windows Event logging, WDDM,
SuperFetch, ReadyBoost, ReadyDrive support, WPF, WCF, and on and on
(thousands of new features).

But what about the end-user experience that people may not have
heard of? Below are 10 improvements in Windows Vista you probably
haven't heard about.

#1 A truly multithreaded explorer.  In Windows XP, if you opened a file dialog or a window that had to connect to the CD/DVD drive or to the network the whole shell would hang while it did its thing.  Not so in Windows Vista.  In Windows Vista, that all is done in a background thread.  Getting around the OS is always a very fluid experience.
#2 Wireless networking is much improved. The built in wireless networking in XP was pretty awful. Most users ended up having to a user a kludgy or bloated third-part wireless network manager instead.  The one in Windows Vista is not only better looking, it "just works".
#3 Incredibly good plug & play. While it is true that video driver support for Vista at launch was spotty (and not to say "I told you so!" but...read this article from over a year ago). The reality is that most things do work and work extremely well. If I buy a brand new device today and plug it in, odds are it'll work without me having to do anything. And Vista has a nice little progress dialog that you can check to see how your new device is working. On XP, you just got little pop up messages during every stage.  And how many times on XP did you run into something just not working when you plugged it in with no real explanation? That won't happen on Vista. At the very worst case, you'll be able to see where things went wrong in the progress dialog that you can look at.
#4 More polish. Polish matters. If it didn't, we wouldn't be talking about the iPhone all the time. A good user experience matters.  Look at the screenshot to the right here.  Don't be afraid.  This is one of the reasons why Jenny Lam is my hero (her team at Microsoft really did a great job on this).  This kind of improved experience throughout the OS makes Windows Vista much more pleasurable. While there are plenty of people who use our software to make XP look a lot like Vista, there's no substitute for the real thing.
#5 More information about your system. A lot of us have big giant cases under our desk. In fact, in the age of the monitor having the USB ports, the case is getting farther and farther away from us. So the days of being able to simply listen to the hard drive crunching are long over.  On Windows XP, if my system was slow, I'd bring up the task manager and check CPU. And if the CPU meter wasn't pegged then I'd go and look at the case to see if I could hear the hard drive crunching.  On Vista, the task manager will tell you how much of your hard drive bandwidth you're using up and tell you what process is accessing the disk.
#6 Much higher tolerance for handles.  On Windows XP, if your system runs out of handles, programs won't launch and weird things start to happen. There's no warning message about it. Almost nobody knows what a user handle is. On Windows XP, users would just reboot their machine.  People who know what handles know how to kill them off. I wrote an article "How to keep Windows XP stable" that goes into this. On Windows Vista, the system seems to do just fine with high handles so far. This means a much more stable experience.
#7 Assessments. If you're reading this, you're probably the person who people call with computer questions. On Windows XP, you might ask them "What kind of computer do you have?" and the likely response was "It's a Dell." or HP or Gateway or Toshiba or whatever. On Windows Vista, you instead ask them what their performance index is which they can get to very easily. This instantly lets people see how fast their computers really are.
#8 Better thumbnails. Windows Vista has "Windows Photo Gallery". But 99% of the time I'm going through photos in Explorer.  In Windows XP, my choice was "thumbnails" which topped out at 128x128 thumbnails.  In Windows Vista, I can have them as large or small as I'd like which can make for very handy viewing of lots of pictures at once.
#9 Better Laptop experience. In Windows XP, I didn't ever know for sure if my laptop was really going to come back from sleep or hibernation. Some of my laptops still run XP and it's a difference between XP and Vista I am constantly reminded of. In Windows Vista, my PC is definitely coming back from sleep. I know there are still people who complain, I'm not saying it's perfect but it's a lot more reliable for me than XP was (or OS X Tiger was) in this regard.
#10 Usability improvements. There are so many tiny touches in Windows Vista that you won't see mentioned anywhere. For instance, in Windows Vista, if you click on the system tray clock, you get a nice calendar dialog. By contrast, in Windows XP, I would double-click to get the date and time properties and it was slow (the Vista calendar pops up instantly).  It's just a nice small but useful touch. The home folder is a really nice touch that wasn't in XP in a meaningful way.