Being the technical geek that I am, I've given Windows 7 the  proverbial shakedown cruise to see what I was going to be up against at  work when we start getting the new PC's.
I'll admit, I was not  expecting much: my enthusiasm being shot down in flames by the Vista  rollout had me very skeptical about Microsoft's direction and vision  when it came to operating systems.
I performed both a clean install and an upgrade installation from Vista to see how the experience was in each case.
I'm  not going to go into all the differences, enhancements, and tweaks you  will find in the OS; there are plenty of sites on the web where you get  that info. Instead, I am going to focus on the installation experience,  and first "out of the box" experience.
THE CLEAN INSTALLATION
The  clean installation of Windows 7 was undoubtedly the simplest install  I've ever had with a Microsoft product, and it is clear that they have  been watching Apple closely as far as how they streamline every aspect  of their products. A fresh install of Windows 7 is just as easy and  quick as a fresh install of OS X on a Mac, and was finished well within a  half an hour.
Excellent!
THE UPGRADE INSTALLATION
The upgrade installation took much longer: about 3.5 hours.
I  have had bad upgrade experiences in the past, and prefer a fresh  install of an OS so it doesn't carry through the quirks of the prior OS.  With that in mind, I these are the steps I followed to upgrade my Vista  machine to Windows 7.
Ran the Windows Upgrade Advisor to see if there were any problems or conflicts.
As  my upgrade PC was only about a year old, the only problem reported was  that McAfee AntiVirus 8.5i was incompatible with Windows 7. That was not  really a surprise to me --I had already been looking at different  AntiVirus solutions-- so I uninstalled it.
Performed a general cleanup with CCleaner.
If  you don't have this handy freeware utility on your computer, get it  now! CCleaner (allegedly for "Crap Cleaner") is a small tool that does  three things: deletes unused temporary files, cleans out all invalid  registry entries, and allows you to manage the programs that startup in  the background when Windows boots.
Running this type of cleanup  prior to an upgrade is a good idea, as the new OS transfers all your  settings and files from the old OS.
Needless crap will only make any upgrade more difficult.
At best it will make the upgrade take longer.
At worst, the installation might fail.
After  I cleaned the files and registry, I looked through the programs that  start up with Windows and found a few that I don't really need to have  running (iTunes services, etc) and disabled them.
Re-booted and made sure everything was still working well.
Just a precaution to make sure I didn't turn off something I needed!
Run the Vista Disk Defragmenter
This  step is likely not necessary, in all honesty. I've always done this in  the past prior to doing an upgrade, so it's a habit for me.
However,  I ~believe~ that Windows 7 handles upgrades differently: instead of  just writing over the old OS with new system files, it actually copies  the files, folders, and settings to a protected area, does a FRESH  installation, and then ~imports~ your data back into the new OS.
(If I am wrong on this detail, please let me know!)
Re-boot, then ran the Windows 7 upgrade.
After  answering a couple questions at the very beginning, Windows goes to  work. Obviously, the more stuff on your computer, the longer this  process will take. I've heard reports of anything from 1 hour to 8 hours  for an upgrade.
If your computer isn't a fresh squeaky-clean  install of Vista with nothing else one it, plan on setting the computer  aside for a few hours.
THE WINDOWS 7 OUT-OF-THE-BOX EXPERIENCE
I  am wholly impressed! If you are already used to Vista's interface, then  there really is not much new visually in Windows 7. However, it feels  like they've taken Vista, streamlined and stripped all the bloat and fat  off of it, and what you have is a leaner, faster, and more intuitive  interface.
There were a couple items that surprised me... The much  touted "Windows Mail" that was part of Vista is gone. If you used  Windows Mail, the upgrade will save all your mail and contacts and allow  you to import it into Outlook.
Windows Movie Maker... gone.
Windows Photo Gallery... gone.
If you were running Windows Ultimate Extra and using Dreamscapes for an animated desktop... Kiss it goodbye.
Some  of these apps were heavily advertised not even 2 years ago, as  Microsoft was trying to complete with Apple's approach of including  everything the average user needs right out of the box. Windows has long  had a particular reputation: buying the PC was the easy part, and  spending the next few days purchasing and installing all the stuff you  need to ~use~ the PC was the hard part.
So why Microsoft has  decided to backpedal on that marketing decision is an interesting  question. However, at the end of the day if I am going to spend my  hard-earned cash on an OS, I'd rather have a slim and sleek OS that  needs some apps install (that ~I~ get to choose) than a bloated one that  contains apps I probably don't need.
Fortunately, most of these excluded apps are available via Windows Live Essentials and can be installed after the upgrade.
Both  the fresh install and the upgrade performed equally well. There were no  quirks, sluggishness, or broken applications on the upgrade  installation.
All in all... Thumbs up, Microsoft! This is an OS done right. The PC is ~finally~ nearly as fun and easy to use as a Mac!