N9 has a much weaker GPU than last year's iPhone4 or SGS1. Basically, N900 and N9 has nearly the same SoC except the CPU frequency and power efficiency. (which can also be equalled by overclocking the N900 to 1GHz or faster) This was done to speed up the production of the N9 as Maemo/Harmattan was built on OMAP3.

It's a hardware limitation and not something software can improve. N9 won't be able to decode high profile 720p x264 videos due to its weak DSP while N8 can do some of it. N8 is actually more capable than the N9 in terms of media consumption. (better DSP, FM TX, HDMI out, stronger bluetooth signal, louder speaker, better music player etc) So yeah, N9 doesn't deserve the N8 successor "N" series badget IMO. It should have been called the M9 or something. =P