I've just installed Win7 on my Lenovo S10 - installation could not have been easier. I popped it onto a USB drive and had the full install completed in about 30 minutes.

The Lenovo (1.6GHz/160GB/1.5GB) runs perfectly. I did not have to install a single driver myself, and even Bluetooth works as it should.

I'm still running into too many apps on Win7 that don't work, so MS clearly changed a lot under the hood...