strangely enough, since my n900 is not just a printout, my phone is also 3d, so i'm not that fascinated with your phone as you obviously think everyone should be...
I keep an extra battery on my wallet all the time. It has saved me a few times. Definitely a good thing to have. And it is fun to change your battery when iPhone users are watching.
"Problem" is that I like to use the pen with my N900. the N9 doesn't have a pen anymore and - correct me if I'm wrong- is finger optimized and won'T work well with pens -- or does it?
l
I think my choice of next phone is going to be largely based on quality of camera.
That's like picking a car based on the stereo in it...
To the OP: If you like the N900, and it's just the battery giving you an issue, buy another battery. I went through 3 batteries with my N6230 in the 5 years I used it. New batteries can be had on-line for quite cheep, there's a thread on here about ones that have better capacity than the stock one even.
If you're looking to hop phones, I doubt you'll find one like the N900. It's pretty unique in what it is and what it can do. When you do go... are you going to sell your old N900? I'm sure some folks here would love to buy a spare.