Well I think there is always need for improvement, big or small. One thing that really bugs me made me start this thread. Let's see what else other people have to deal with.

What I think should improve:
Being able to use the N900 without any suite. Offer the right (cable)drivers in a easy way (because their site really doesn't!).

And second:
Make tools for the capabillities of the phone. I really like the video on the phone, so I like to have some short clips on it every now and then. A simple FFMPEG interface with something like: ffmpeg -i CL1048.flv -r 25 -ab 128k -f mp4 -b 800k -s 800x480 CL1040.mp4 would greatly enhance the experience.

You need a suite to use it? I don't (except for transferring data from 9300i to N900)

ive never used a suite.
usb cable/mass storage or ssh is all i've ever had to do.