My main memory of Maemo (I ran an N900 for close to a year, my first smartphone after a couple of Motorola feature phones) is that the features I would have needed to get a decent user experience were never completed by Nokia. There was never a proper app store, the navigation app was close to useless, it didn't integrate well with Nokia's desktop software, etc. And then they just abandoned it.

As for the OS itself, I just remember being surprised at how what seemed (naively) to me to be a lot of RAM for a small device just wasn't enough. Hardly a fault that was unique to Maemo, though. So much bloatware today...