I've used a lot of different PDA's, smart phones, and BlackBerry's....and the one thing that I personally don't like about the new Nokia is how thin it is.
My handheld of choice is a 7290 from RIM. Keys are nicely spaced, space bar is nice and big (like a normal keyboard) and the device itself isn't so thin that I'm trying to type on a piece of paper...my fingers curve more naturally around it.
My next beef with this Nokia is the location of the * 0 and # keys. The 7290 has the * and # wrong, but i use them so infrequently, i barely notice...but I DO use the 0 key to dial phone numbers. All the other PDA's have the 0 below the other numbers (like where it is on a normal phone) except this one.. Learning curves suck
Now, that said, as long as the Symbian OS on this keeps one thing from previous versions, I would like to see it keep the speed of previous versions. It may be 8 menus deep to find what you want (hope they change that) but going between menu's on a Nokia has always been quick.
And the other thing I'd like to see that Nokia kept is the durability (admittedly, havn't used a Nokia phone in a while). The regular Nokia phones used to be (maybe still are) one of the most durable things I've ever run into. As much as I don't like Nokia phones, if your area of work requires something that can take a beating, I'd always recommend a Nokia.