Depends on what your needs are. First off, N900 being the first Maemo device, I'm sure it is more prone to some issues than say the N97 is. Though, the N97 is not all that hot compared to the iPhone.

But the biggest question is basically how much do you need a full complement of smartphone features? N900 was not designed to be a full-on consumer smartphone. It is a mobile computer with phone functionality. N97 has more features in this regard. And while I'm quite sure most any issues people have the N900 will get fixed (personally I've to have any issues), but I doubt it will ever get all smartphone features. That will be left to N900's successors down the road.

So, if you are expecting a full smartphone features, you bought the wrong phone. If, on the other hand, the computing features are what you want and a basic, good phone functionality, N900 might work out for you.

But the best audience, in my opinion, are developers and gadget freaks who love the novelty and mobile computerness of N900, not those expecting a solid, ready smartphone experience.

Edit: Clarification - N900 is the first Maemo device with phone. Of course there were the Nokia tablets first.