Now is a great time to get back into the PSP, a lot of great games have come out in the last 6 months and more are on the way.
Portable Ops is a mixed bag. On one hand, it is directly related to Snake Eater, and it looks fantastic for a portable title. The multiplayer is also fun, a lot like MGO. On the other hand, the controls are very limited by the lack of a second analog stick, so at first it's like wrestling with a fucking bear to get your character to do what you want. The squad building feature is addictive as hell too. I'd say go for it, just expect to deal with some strange controls at first until you get used to them.
Jeanne D'Arc is fantastic, kind of a slightly less complicated Final Fantasy Tactics type game. Definitely worth a buy.
Dracula X.. that's a no-brainer. Get it.
Monster Hunter Freedom 2? I can't recommend this game enough, but there are some things to expect with it. It's a hard game, but it's rewarding. There are hundreds of items to create, dozens and dozens of quests to do, and multiple zones to explore. The graphics are very good for a handheld title, and the music is fantastic. Building up your Pokke farm is also a fun little diversion from the hack and slash, and it's worth every point you invest in it as you can only get some rare items from the farm.
But the real meat of the game, they wyvern (dragon) hunting is where it's at. It can also be the hardest and most frustrating. You can only go so far alone, some of the tougher ones will require 1-3 additional players. That's where the ad-hoc mode comes in. If you have local friends with PSP's and MHF2, your enjoyment of the game will shoot up immensely. Otherwise, look into a Datel Wifi Max and use Xlink Kai to play online. If you stick to solo offline play, you'll be missing a huge chunk of the game's content.
Kirk Foiden is set up to play online, and I will be within a week or so. I'd be happy to meet up with you or anyone from NG.com for that matter.
Also, don't forget that Final Fantasy Tactics just released for PSP last week. Other than a little lag during magic attacks, it's an amazing port. The old dated looking CG cutscenes have been totally replaced, and the game's dialogue has been improved. A definite must buy.