My advice would be (if you have cash available) is to first buy what you think is your best alternative, and try to use it for a week or more, and see if you miss the N900 or some of its functionality or not. If you do, sell the alternative, else do it with the N900.

The initial reason i had to buy the N900 was about its potential, and time showed me that i was right. Now is a far better device than it was then. And could keep improving. But your milleage may vary.