I use this on my R60 ThinkPad (slightly bulkier, more plasticy version of the T60).
It is good; it is one of the lighter desktops. Still feels a bit heavier than Windows XP but does ultimately allow you to run more recent versions of everything.
My only issue with my GPU (and old Intel GMA 945) is not very well supported by the OS anymore, especially in the web browsers it is very slow with lots of black / graphical corruption. It tends to be better to run the browser itself in software; i.e:
$ LIBGL_ALWAYS_SOFTWARE=1 chromium
It could be that the xf86-video-intel is not being used and the modesetting support isn't well maintained for such an old GPU but I didn't want to spend too much time fiddling.
One unlikely OS that I find very, very good on this era of machine (too new to send to landfill, but too old to run "modern" bloat) is OpenBSD. If you can accept the spartan installer (which is very easy btw, if you look at it objectively), it provides a clean OS with X11 and FVWM to get you started. Firefox and chromium are available.