It wouldn't be too far off the mark to describe Hot Wheels Ultimate Racing for the PlayStation Portable as a no-frills knockoff of Need For Speed Underground. The game lets you collect, decorate, upgrade, and race Hot Wheels toy cars on a number of outlandish courses. Generally speaking, the racing action is solid. However, there aren't a whole lot of different tracks or competitions, and the 3D graphics don't hold a candle to A-list racers like Ridge Racer or Wipeout.
Races take place on intricately designed fantasy courses that feature multiple paths, jump ramps, and the occasional flaming hoop or piece of rampaging construction equipment. While driving, you can kick in a nitro boost or activate a slow-motion effect. You have to use the nitro and slow motion frequently in order to successfully clear most jumps. Every time you nail a landing or speed through an obstacle, such as rocks or land mines, your nitro and slow-mo stores will be replenished. While there's nothing here you haven't seen in other racing games, the sense of speed brought about by the nitrous and jump ramps is very satisfying.
Another aspect the game borrows from Need For Speed Underground is the ability to collect different cars and unlock new parts and paint schemes as you work your way through each competition. You'll need those upgrades, too, because the CPU drivers in Hot Wheels Ultimate Racing rarely smack into the rails or slow down. In fact, they're so tough to beat early on that you'll probably spend an hour or two just trying to win the first competition in the challenge mode. Thankfully, the difficulty becomes manageable once you unlock the first set of engine and nitrous upgrades.
In total, there are approximately 30 different cars to collect. They look like 3D renditions of actual Hot Wheels toys, and you can change their paint schemes and decals to some extent. During the race, it's sweet to watch flames shoot out of your car's engine and sparks fly whenever you nudge a rail or another car. The courses also feature a good variety of animated touches, such as prehistoric birds, steaming lava beds, and falling rocks. Unfortunately, aside from the jump ramps and falling rocks, the courses aren't actually all that interesting. The textures are simple and muddy, and there aren't many identifiable landmarks along the raceways. As for the audio, it gets the job done without much fanfare. You won't remember the engine noises, metallic crunch sounds, and futuristic music after you shut the system off, but they're fine otherwise.
The game's biggest problem is that it's sorely lacking content. There are only six competitions in the challenge mode, each lasting three races. Once you manage to beat the first one, it won't take more than an hour or so to complete the rest. Besides the challenge mode, you can kill time with the usual assortment of quick-race, survival, and time-trial modes. That's nice, but there are only 11 different tracks in the whole game, so those modes won't hold your attention for long. You may get some extra mileage out of the multiplayer mode, assuming you can find someone locally to play against. There's no manner of online connectivity--not even a way to download additional courses.
Hot Wheels Ultimate Racing isn't a bad game by any stretch, but you should probably pass on it unless you're a Hot Wheels fanatic or have a pathological need to get another racer for your PSP. Considering how many racing games have been produced for the PSP, you can easily find one that's flashier and offers more variety than this one for the same price, or cheaper.