Before you buy a n900. NOTE the following downsides:

1. Nokia has extremely poor record of device support across its multiple devices. After a few updates, the device is usually forgotten (see previous "n" series)
2. No Meego for n900. Only an open community port will (if) be available sometime in the "future". (see point 3)
3. Open Community OS development has a poor track record on Nokia devices. See attempts on previous devices in the "n" line.
4. NO mobile support from major app vendors. There is no google maps, there is no adobe flash etc. If you want these apps, forget the n900, it will NEVER get it (even the Opera release was an unofficial hobby project by the devs who make no promises and cannot officially promise future versions and fixes).

If you are a technically oriented person who likes to tinker and write your own stuff in linux, love to install unofficial apps and experiment (many of which can brick your device) and is happy with the state of the n900 NOW as of PR1.2, then the n900 is for you. No other phone is better for this user.

If you are NOT a linux geek and rely on official support and are just attracted to the N900 for its browser/web experience/multitasking, then do NOT get the n900 as the n900 web experience is going ot be inferior to other devices soon (no flash 10.1, n900 is starting to lose access to sites that block lower versions of flash). Other devices are catching up and will surpass the n900 for the web experience soon.

Lets be clear - DO NOT buy the n900 with what you HOPE it MIGHT become, only buy the n900 for what it is NOW. Assume for all intends and purposes you will get NO future support in terms of bug fixes etc.

If you are OK with that then buy the n900 for sure.

Otherwise stick to Droid phones etc which cater to a normal user base and provide proper support.