EDGE is the biggest limitation for me. I'm getting my 8525 soon, and hopefully 3G will be up in my area before the end of the month. I'll see how much 3G I am actually using compared with WiFi, and then when the iPhone comes out, I'll be able to make a more educated decision.
The educated decision also applies to the keyboard. As I said earlier, even with my limited Apple experience, my history with the iPod and related products has proven to me that Apple understands UIs. That's a non-issue for me until I see that it actually does or doesn't work as easily as intended.
No SDIO? With 8gb available, how badly is it needed? The biggest micro-SDs are 1gb, and the biggest minis are 2gb. Even the 4gb version is a HUGE LEAP by comparison.
3G would be nice, even if only to make me feel like the device was more worthy of it's sticker price. The same logic holds for the expansion slot - not necessary, but nice. As far as I'm concerned, this device is a winner for 85% of the population who can justify it's cost. It seems that I fall into that category. Give me a calendar, a good phone, QWERTY, email, and web-browsing, and I'm happy. Give it a slick interface like this one (assuming it's nearly as good as it looks), and I'm happy as can be.