If you are expecting a Diablo type game, Monster Hunter does not fit the bill. If anything, Monster Hunter is more like Demon's Souls, if you've ever played that. I haven't played Monster Hunter Freedom 2 in a long time, so some of this information might be erroneous.
First off, there are no levels in Monster Hunter. It's all about your equipment and the items you have prepared. And the combat relies on timing, like Demon's Souls. Just trying to run in and blindly attack enemies will probably get you killed.
Second, the loot system is nothing like Diablo. In Diablo, you were constantly getting tons of new equipment, and each new piece of equipment could have random stat bonuses. Monster Hunter is again, like Demon's Souls in that the items that monsters drop are mainly used to upgrade your weapon. You aren't going to kill a creature and get an awesome new Long Sword of Fire damage with +10% to hit chance. You are going to get a bone that you can use to turn your sword into a bone sword or something. Also, the equipment set is more like Oblivion and Demon's Souls than Diablo.
And for the Monster Hunter fanboys, yes I know Monster Hunter predates Demon's Souls. I only bring up Demon's Souls because he has a PS3, but no PSP or PS2 to try the previous Monster Hunter games.
I highly recommend you try the game before buying if you can. I couldn't get into Monster Hunter Freedom 2 on the PSP. Part of it was the controls, but part of it was that it was just a lot of grinding for materials to craft a new weapon to help kill the next enemy to get even more materials to get an even better weapon. It just felt a bit repetitive to me. And considering that the story is basically non-existant in the game, I lost interest pretty quickly.
