No multi-touch is a shame.
I have read that Android can support multi-touch, but hardware developers will need to come up with their own drivers first.
I too was a little unimpressed with the G1. Maybe my hopes were too high? I'd like to see what it looks like by January however once the 3rd party stuff starts catching up.
I can't comment on multi-touch, I really don't know the design/business issues there.
The G1 is a first of the type, and there's a lot of hype around it.
The thing I see with the Android stuff is this.. It's not going to convert iPhone users, there is too much bling and brand loyalty there. Android will do much more than the iPhone simply because it's not going to be tied to one company.