I got Daxter yesterday as an early birthday present and am about 17% through it so far.
This has to be one of the best games I've played on my PSP yet. It takes alot of the fun stuff from the Jak series and applies it to our furry little Ottsel.
You can crawl, and are given an electric bugswatter and spray gun that apparently gets upgrades much like the guns in Jak II and 3. You can drive vehicles as well and the dream sequences are hilarious. You start with the Matrix one (which unlocks a spin move) and a Braveheart one gets unlocked after that (completing it gives you more health) and there are a few others.
Although developed by another studio this has the complete and total feel of a Jak game. For all those wondering about firmware, it's 2.60 on the UMD. I'd already gone to 2.6 so I have no idea if it'll require you to upgrade or not.
The one thing I love about this game and I cannot stress this enough, like Jak II and 3, there are NO LOAD TIMES after you get past the title screen. This game runs smooth and the dialogue is hilarious. If you don't have it already, do yourself a favor and get this game.