Last week I installed Windows 7 32bit Ultimate on my two-year old Acer M1641 desktop, it was a smooth process. The only unrecognized device of the original PC after the Win7 installation was a mysterious "co-processor" device. After installation of the Nvidia NForce chipset driver everything on the original PC was recognized. The added old Compro X50 PCI TV/FM card was also not recognized. Luckily Compro provides the driver and necessary applications for this 5-year old product.
There was a glitch, after the installation, the grub bootloader is gone, only Vista and Win7 are shown in the Windows bootloader. So I have to recover the grub bootloader so that I can boot into various Linux versions (Ubuntu 9.10 32bit, Ubuntu 10.04 64bit and Arch Linux).
I am now using Windows 7 Home Premium 64bit for my Asus laptop. Same as the experiences there, I do not see too much differences between Vista and Win 7. Being a new installation with less "junks", it seems to be a bit faster.
Other than that, one of the major difference is the XP mode. The nice thing about XP mode is that now it supports USB. This is not a fast PC to run the virtual XP mode since it lacks the Hardware Assisted Virtualization Technology feature and the amount of RAM is not that big. Still allocating 512MB to the XP mode seems to let the virtual XP run relatively smooth. But this is just a test and I do not really need XP or miss XP.
Overall, the first impression of Win 7 is positive. But heh my first impression with Vista was also not bad even though many people have negative views on Vista.