I would say the same... boot to OS 9, trash everything X and be done with it.

Or are we missing something here?

I do have Tiger on my iMac and while not exactly snappy, it runs pretty good. 500mhz, 512mb RAM, 80gb HD. Maybe you're short on RAM?

I use Safari 3 for web browsing, anything newer (Safari 4, Firefox 3) feels too sluggish.