I've seen using Win7 since the BETA.
I love it, especially for laptops. For my job (SMB Consultant..small/medium business computer/network consultant)...I use my (primary) laptop all the time going onsite to clients. My laptop lid simply get shut, opened, shut, many time a day, stuffed in my laptop bag, office, home, and boy did they do a great job with hibernation/suspend power management. I think my laptop truly reboots once every 3 or 4 or 5 months. Else, 99.9% of the time it's suspended/hibernated and woken up.
For desktops...I also love it. Not that I had a problem with XP, but even so, stability wise it's even more stable. It just runs and runs, I reboot that perhaps every couple of months due to critical updates that require it. My main office workstation is still running Vista 64.
Windows 7 is a wee hair quicker than Vista...sure when Vista came out it was very doggy, but as service packs and many other incremental updates came out, performance slowly but steadily improved. Plus..back when Vista came out, many people still had single core early P4s, and the fake dual core (hyperthread) P4s...which were barely up to the task. Fast forward a few years to current times, and most of those old rigs are long gone to the boneyard, with pretty much all processors now true multi-cores.
On dual core or higher, with 2 gigs minimum for RAM, it runs great. If you're a power user or gamer, shoot for 4 gigs of RAM (or more if you're a super power user...go 64 bit Windows so you can use past 4 gigs). If you have an old app that needs XP mode, ensure you get 4 gigs....and a quad core is better, as XP mode is really just a virtual machine..so your hardware is running two OS's at once. It's just a special version of VirtualPC.
As for legacy software, I've not come across many that won't run in Vista/Win7. Most of those that have a quirk can run fine just by right clicking the shortcut and setting the compatibility mode, and/or "run as administrator". There is some software I've seen, mostly line of business apps and accounting apps, where an old outdated version won't run on the newer OS's, but since LOB apps or accounting apps are important, you should be running a current supported version in the first place.
Out of my 7 computers at home, only 2 still have XP...one of those hasn't even been turned on in months. The rest of Win7 and a few *nix distros (Mint and OpenSUSE) (technically another running a linux security gateway distro called Astaro)
Just for kicks, at the office we have an old Dell, some mini Optiplex model, GX260 or GX240 I think, it's an early Pentium 4 2.4GHz, has 1 gig of RAM, onboard Intel video...we installed Windows 7 on that, and it actually runs about as equal as it ran Windows XP. It may take a little longer to boot up than it did with XP, but once up and running, it's quite usable for basic stuff..surfing the web, etc.
Windows 7 is so much easier to use and setup with peripherals too, printers, scanners, cameras, phones, etc. We are at the time were we'll see less and less support in hardware for WinXP, so there's another reason to catch up. Windows XP was great, it lived a longer than usual life for a Windows OS. But it's currently 3 generations old now. Windows 98se was great too..back in it's time. But sometimes...it's time to move on, newer and better ones have come out. Make the move!
Although I'm not overly fond of HPs laptops, I do still like their printers. Granted many of the multi-function ones tend to have extra bloated drivers, but the printers themselves are still good and one of my recommended brands.