#61 is funny... I would not suggest putting W7 on "everything," unless your everything has at least 1GB (or better, 2GB) of RAM.
I do have it installed on a P3 750Mhz with 512MB of memory and as a quick "benchmark" that I just did, it takes 70 seconds to get to the login screen from being completely shutdown.
On my 2Ghz laptop, it takes 35 seconds to get to the login screen.
Now, since the P3 750 is in a different room (the junk room), I do not use it as a daily tasker. I also do not consider 70 seconds to the login screen "fast", but taking into account the age of the system, yeah, I think that is not bad either.
Now, with that said, my three year old laptop (came with 1GB, but I installed 2GB a couple months ago) runs W7 just fine (minus Areo). When I tested Vista on it a couple years ago, it ran like total crap. I actually became used to the sluggish response of certain tasks that I did and after it hit retail, I decided not to buy Vista for it and put XP back on. Wow, did it feel like a new laptop! The sluggish response all went away and it really did feel like I brand new system. Granted that I went from 1GB to 2GB since then, but that alone is not enough to completely change the experiences that I had (when the particular tasks that I was doing had nothing to do with system RAM).
With W7 currently installed on it (and forcing myself to test various things out with it and not bounce back to XP), I am actually sticking more and more to W7 and it does fine for what I use the laptop for. Probably would be considered "normal" computer usage patterns.
Yes, W7 has improved (greatly from Vista) and responds to most things as fast as XP does, but tread lightly with running out and paying $150+ for an OS that may not meet your expectations on a few generations back hardware.