Yeah. I have to do a lot more testing also as it seems it can play some 450p main profile H264 while it can't some others with same profile. (It may have something to do with bframes as you mention but not sure right now. Haven't really compared the media info fully)

btw, I am now able to play the same 720p H264 base profile video on my N900 after the recent hack. Very impressed as it plays it perfectly smooth. (even without overclocking the DSP) But yeah, it doesn't look as nice as watching it on the bigger and better N9 AMOLED. =P

Anyways, for those who want universal video playback of everything you find on the internet, N9 is not the phone you want. It's the SGS2 as it's the only phone that can play everything you can throw at. (well, even the SGS1 or the old Galaxy Tab 7" also) Samsung sure knows how to make video watchers happy on their mobile phones. (even their default player has built-in brightness control, child-lock function etc etc) Nokia doesn't seem to really care on the other hand and just makes a bog standard video player.