If you haven't played any of the others in the series, then jump on into this one. It brings the best of all the previous games and wraps it all up into one awesome package.
An estimated 300 - 400 hours game play if you are looking to clear every quest (might as well). Multi-player is very well done via wi-fi (local), and if you can, it is playable over X-Link Kai (PSP online) which opens up a whole lot more fun, playing with friends or random hunters from all over the world.
The thrill of battling against wyverns, dragons and ferocious beasts is the main attraction. And taking down something ten times your size is very rewarding. There is a good selection of weapons and armor to utilize. From massive swords to bows and bowguns.
IMO it is a must have PSP title. I just can't get enough. To date 400+ hours on MHF 300+ hours on MHF2 400+ so far on MHFU
"when all else fails... RUN AWAY!!"