While it hasn't been tested yet (for obvious seasonal reasons), forecasted snowfall quantities should show up in the trend graph this winter. This doesn't completely match your suggestions though, so we'll take this into consideration moving forward.
I agree that alerts remain a critical feature we have yet to implement. At this time, we are waiting for Apple to finish completing their push notification functionality for iPhone applications. Until push notifications are ready, we really can't add this feature "the right way." It was originally thought that Apple was going to have push notifications ready for iPhone OS 2.1, but recent rumors have noted that may not be the case. We're anxiously awaiting this feature as much as anyone else though.
The advantage to seeing snowfall projection maps is that you know where it's going to snow heavily. That information isn't readily really there when you can only see a number for a named area in your list. A map gives you an idea of the size of the system. The same analogy is looking at a radar map vs seeing .5 inches of rain at 4pm.
I'd also very much like to see the last download/forecast and all data remain in the program. If I don't have a connection I'd like to see what was last there.