You ought to give CyanogenMod a try; it's breathed new life into my G1. I installed it yesterday after my home screen's several-second rendering time pushed me over the tipping point.
It's easier to install than it seems, noticeably faster/smoother, and the Browser and Gallery apps both support multitouch.
It's easier to install than it seems, noticeably faster/smoother, and the Browser and Gallery apps both support multitouch.