1) As of right now, there is no software on the device to send/recieve mms. There has been discussion about adding this, but it isn't possible right now, and there hasn't been any official word about when/if it will be available. Some people have suggested email as a (better) alternative for sending pictures, etc.
2) It has a webcam on the front, but I don't think video calling is enabled yet. I think it's being worked on though.
3) People will give you different answers to this question. It has many advantages over the iphone that I appreciate (open development,crisper screen, hardware keyboard,...), but other people may find that they prefer the iphone for various reasons.
4) It's a new device, so there will be some rough edges. Even the iphone, which a lot of people treat like the holy grail of "smartphones", didn't start off with it's app store, had no mms for years, and still has lots of controversies. I don't have a device yet, but most of the issues do seem to be software issues more than hardware issues. Don't expect usb host mode, since that may be a hardware limitation. I would recommend a screen protector.