I just installed Win 7 32-bit Ultimate on my work laptop tonight (Dell E6400 with 4GB RAM). Everything worked right out of the box, except video quality was poor (downloaded the Nvidia Quadro 160M from Nvidia) and had to install the Synaptics touchpad driver
to get my mouse moving anywhere near fast enough. Everything else worked right after the install.
I had to do this as a dual boot, so I did the "install Windows 7" as an expanding VHD file and thus far the performance is fantastic. Totally outperforms Vista on this machine...and runs on par with the Ubuntu 9.04 install that is also on this laptop.