N900 has no calling and disconnecting button. Display is nice and big. Battery too is very good. But as all in touch phone consumption is fast when used extensively. Use for continuous four hours will consume the battery, so do keep a extra battery(BL5LJ for 900 bucks) ready, or keep charger in your bag.
the phone operates on firmware Maemo 5, which is LINUX base. Numerous applications are available. Famous Mac OS and android applications are also available.
In the beginning phone may be difficult to use, but after you get accustomed its nice.It has motion senser, and Light Sensing too. enabled with QWERTY pad, its excellent to use.
Only cons :1. Its bulky. 2.sometimes it becomes difficult to answer the phone when you are watching a movie and you have a incoming call.
Best boon is maemo.org, where we can get any bits and pieces of information.the community is excellent and very helpful. You just ask for help and there are dozen of people to help you.