I used iTerm before Leopard, but it crashed at least once a week, and sometimes it would just forget settings, and it used up an insane amount of resources if you left it open for a few days (and shutting down all my ssh sessions and restarting them is not my idea of a good time, nor is trying to figure out where I put this server or that server in the tab list; I like them to stay at the same position so I don't have to consciously think about that).

When Leopard came out, it had a Terminal.app that fixed essentially all my issues with the previous Terminal.app, including having tabs, etc, and it hardly uses any resources at all, and stays open without crashing for weeks at a time (in fact, I don't think I've ever managed to crash it). Now that there's a copy-on-select plugin for SIMBL for Terminal.app, it's just about perfect.