N900 was a beast of its time, compared to Samsung Galaxy S II which is somewhat a beast of todays era its quite hard to compare. Whilst both offers a wide variety of options to the end user, at the end of the day for me it seems N900 is a little more open in terms of raw hardware access, booting into other platforms (as long as its supported) easily, and best of all it features a proper hardware keyboard. The N900 (as you would have already realised) is more of a geek's toy than to using any of the android devices would make you more of a geek. Both N900 (as well as maemo devices in general) are usually packed full of cool stuff. This is not to say that for instance Samsung Galaxy S II doesn't however the answer does speak for itself apart from comparing an old toy to a new one.

On this slightly biased (towards maemo) forum you'll find users like myself tending to prefer recommending maemo based devices. N900 by a long shot may seem like a smartphone, it may act a little like a smartphone but it lacks some of the features that a smartphone would regularly feature, thus as a pure smartphone it would not function perfectly as such one. N900 is more of an internet tablet as I'm sure you would have heard at least one other person mentioning that it is, for starters you could see that N900 provides you a stylus which you generally would not see being offered on any other regular smartphone devices. This is not to say that N900 is not fit for performing smartphone duties or as required on a regular day-to-day basis however you'll find that N900 being marketed as a smartphone is kind of like a square peg in a round hole.

Another thing to note here is that N900 is no longer loved by nokia. You could say that it is somewhat basically disowned. nokia no longer provides much help for N900 owners apart from security updates and no longer manufactures N900. Apart from N900 which maybe manufactured with hardware defects such as faulty microUSB port that can be easily broken, others faces issues such as things that plug into the A/V socket (usually wired head{phones,set}) can be faulty or even SIM card being unrecognised despite it was working before. Should you encounter a faulty N900 either because it was abused or because it was made with defects, such issues generally has to be remedied by yourself as handing N900 over to nokia care would not necessarily mean that you would see your N900 or a replacement N900 back.

Last but not least, on the discussion of N9 it would be great if N9 was actually made with a hardware keyboard and would not feature things such as aegis (DRM/security measure) however the reality is far from what was highly anticipated by the maemo/meego community.