It matters on the type of user you are, really. I had a N900 and got rid of it because of a few things that I couldn't really live with. As an AT&T customer, living on the EDGE network (get it, Livin' on the Edge) was an issue for me. Same for the screen, it's slightly under my threshold of what I'd call a comfortable screen size for me, but it packed a lot of resolution and sharpness.

The N9's screen, despite the rampant complaints of it being pentile, et al didn't bother me. In fact, I'd call it superior. No real hiccups whilst answering the phone (another N900 complaint) and it just feels overall as snappy, if not faster than an overclocked N900 with smooth transitions. And that's stock.

It (N900) does have a few apps that just have yet to make the transition, but they're far and few in-between that do not have replacements by now. The N9 feels sleeker in my hands, easier to slide into my pocket and Swype makes up for the lack of a hardware keyboard for the most part. But the N900's hardware keyboard kills the N9 experience though - if I need to bang out some commands in terminal, so be it. I pull out the keyboard, hammer away, slide it back in, don't even think twice about it. Cant' do that on the N9.

Both - to me - have less than superior bluetooth experiences for me... but the edge goes to N900. My N9 has difficulties with my bluetooth car stereo connection and my earpiece every now-and-then. Drives me up the wall.

I won't get into the whole capacitive versus resistive argument, but I'm quite happy with the N9's touch, ,multi-touch and swiping UI. But I'm the type that hates using a stylus if it's not my Wacom Intuos digitizer.

The N9 is far from a perfect phone, but it stepped up Maemo's game in terms of UI in my opinion. It just feels way more modern, fits my workflow like no other phone has at this moment. And the GPS is considerably faster on lock (sometimes) than my N900 ever was.

I personally say research more before you buy, but ultimately, I'd say get a N9. It's a very nice, one of a kind phone.

But I'm a talker on the phone. If you're a programmer/hacker/system admin - avoid the N9, stick with the N900. Trying to edit a vhosts.ini file via the VKB will make you lose your religion (for example).