If you had to use the ~200MHz Pentium to buy something from Amazon though you'd be screwed :)
It's amazing what you can do with some swap and a little patience. ;)
I was using a 633MHz PIII until about 3 y ago, then using it again recently when my main computer died, and its gotten a lot harder (on Linux) over those 3 y.
I always thought that a "featureless" one (one without modern JS or CSS) would be extremely painful or useless, too.