I love my N900 for all that it can do, but it can be frustrating at times. Sometimes, it rings, I pull it out, hit answer, and have a nice conversation. Other times, I miss the call because I'm trying to hit a moving target as the N900 flips between portrait and landscape. Other times, it doesn't even ring.
For everyone who says how many apps the N900 has, think about how many times you've seen warnings on having testing or devel enabled. Enough to scare a normal user or even a slightly techy user away. Without those enabled, there are far fewer apps to install. Think about how many you'd have installed if you only used extras.
Many of the most annoying things about the N900 (for me) involve the closed Nokia apps for which there is no alternative, which makes it no better than (or possibly even worse than) iOS or android.
Personally, I think there were a lot of people that looked a specs, thought the N900 would be a great phone and got one. Or, saw it and figured it's a Nokia, so it can't be that bad. Let's face it, it's not a great phone, not even mediocre. It's so much more than just a phone. IMO Nokia really dropped the ball with support and focusing on MeeGo (which looks to me like it will be incredibly slow getting out of the blocks). So, many people came in with high expectations, and were disappointed, and as such have some "hate".