Don't forget that HTC need to spend time further developing and testing 2.2 with their Sense UI, so this will certainly add time to any release plans they might have.
I think it was an oversight by Google to force apps to internal memory, especially given the fact that most non-iPhones don't have the on-board capacity of the iPhone. Plus it seems that HTC's Sense also uses up a lot of this memory, because my Desire with 2.1 had noticeably less space when I got it compared to my partner's Sony Xperia X10 with 1.6, which I noticed doesn't have a lot of Sony customisation on it compared to what HTC do to their phones.
That said I'm happy with how my Desire is functioning and the number of apps I've got on it for now and as much as I'm looking forward to Froyo, I'm not looking forward to setting the phone up all over again.