UMTS / GPRS / EDGE class 12 GSM radio with link speeds of HSDPA 7.2 Mbps / HSUPA
A user-accessible Micro SD slot expandable up to 32GB. That means you can store lots of movies, music, photos or other kinds of files.
At present, this is a UK-only device (I know, odd ...) but should be making its way to the US soon.
The question is, how usable is a smartphone that's larger than your standard smartphone? To me, the biggest drawback to this device is the fact that its size kind makes it awkward to fit in a pocket. If you're a belt pouch sorta guy then you're OK. If not ...
Another drawback I can see is that holding what is essentially a tablet up to your head to talk could be a little awkward. Again, if you normally use a Bluetooth headset, you're set, otherwise, you're going to have to get used to getting odd looks from people.
An interesting angle to the Dell Streak is that the device offers the best of both worlds of the iPhone and the iPad, but requiring only one data plan. This alone could make it very attractive to those wanting to remain connected when on the move, who want a tablet, but who don't want to be tied to two data plans.
I suggest keeping an eye on Streak ... this could be interesting.