Sure the UI isn't as polished as the iPhone, but it's also nowhere near as expensive! Free on a £35 a month tarrif with 1200 mins and unlimited text/data. Try and get a 32gig iPhone for that!
I've been using symbian phones for years, so for me the UI was a doddle. Everything was where I expected it. It's nice to not have a huge learning curve. Multitasking is something I've had on my phones for over 5 years.
The killer thing for me is that I can install what I like, from wherever I like onto the phone *I* own. Flash works, java apps work. I currently have 3 browsers (nokia's own, opera mini 4.2 and opera mini 5 beta), two instant messenger clients, 3 twitter clients and a wordpress admin app. The wordpress app is actually written in python, so I installed python too. Grand total for all these useful apps £0.
It's nowhere near as bad as the reviews make out. The current V12 firmware has ironed out some quirks and V20 is just round the corner which will bring some polish... I believe V20 is the firmware Nokia intended to release the phone with, but were forced to push it out early by market forces.
Unfortunately everyone will remember the reviews and early firmware (V10) experience, and the N97 will forever be slated. The N95 had a similar birth (I was a first week adopter), but as anyone still using one with the later V31 firmware will tell you, it's a stunning little phone. Yet the only thing anyone remembers about the N95 is "crap battery life", which was a fault with the early firmware and fixed within a couple of months.