An excellent arcade racing experience that is only marred by a few unforgivingly difficult races.
As an arcade racer, this is obviously not a very realistic game (at least in certain aspects). While the cars handle somewhat realistically, you can crash your car several times and not only will it sport no visual damage, it's performance won't be affected at all. This can take away a bit from the immersion, but it paves the way for some seriously exciting racing. The liberal use of physics in the game allows you to forget about the rules of the road and just make it to the finish line first, at whatever cost.
A racing game is only good if it gives you a good sense of speed, and NFSU hits a home run in that aspect. Once you start upgrading your ride's interiors, you'll literally feel the wind in your face as you race around the city, going through many of the game's challenges. Drag racing in particular gives you the highest sense of speed, so much that I felt they were the most enjoyable races in the game (despite the fact they were very short), but overall all the racing modes are greatly enjoyable, thanks mostly to that amazing rush you'll get once you start hitting speeds of 100m/h and higher.
It's not just about speed though, the many obstacles in the street will keep you on the edge of your seat and will add a lot of tension to the races. Make one little mistake and you can kiss your winning chances goodbye. During the latter tracks in the underground mode, you'll definitely feel that adrenaline rush as you try to makes as perfect a race as possible, knowing that's your only chance of winning. And it's on those final races that you'll have the hardest time with this game. In order to make the game more challenging (a.k.a., making life miserable for you), during the final races, your opponents will be much faster than you, regardless of whatever upgrades you have applied to your car. This is pretty stupid if you ask me, since it's the equivalent of the computer cheating on you (changing the difficulty to easy doesn't change things a bit by the way), and believe it or not the only way to counter this is by making you car slower. You read that correct; since your opponents cars will scale to your level, downgrading your car will effectively downgrade their rides too, and for me this was the only way I could beat a couple of the hardest races in the game. And to add insult to injury, several of the final races are multiple lap affairs (6 or 7 laps) across some the largest and hardest tracks, which means that you'll probably break your keyboard (or gamepad, or wheel) out of frustration, when you are forced to reset a race as you make one crucial mistake during the final lap of the race.
But despite this flaws, the underground mode is very enjoyable. Your main goal will be to become the best driver in the city, and you'll accomplish this by going up the ranks. You'll climb up the ranks by beating specific races at a certain time, and if you ask me it would've been much more interesting if the ranks were determined on your actual performances (i.e., your win-loss ratio). There is a loose story that goes along with the underground mode, but it's pretty irrelevant and rather predictable. However the cut-scenes that play out the story are pretty cool, and occasionally hilarious.
NFS Underground offers a tasty visual treat. The graphics are overall very sharp and detailed, from your cars to the city itself. The crowd models are a lot more bland, but that's understandable since the crowd is largely irrelevant. Something that's very relevant though, is the motion blur effect that kicks in as you reach very high speeds. This greatly helps to increase that sense of speed, and while it can make spotting incoming traffic or obstacles a bit harder, it's a great addition to the game. It's a shame that the game maxes at 1280 * 1024, and that it offers no support for AA or AF, since jaggies can dent the impressive look of the game.
The sound on the other hand is virtually perfect. Car engines sound appropriately powerful (depending on the car and the level of customization), and more subtle things such as the crash noises (well, those can never be subtle really), the tire friction, or that whoosh you hear and feel as you nearly miss an incoming car, sound appropriate enough and greatly help increase the level of immersion. The soundtrack of the game is also spectacular, featuring a very varied array of themes, all of which fit very well with the underground theme of the game. My personal favorites were Rob Zombie's "Two lane blacktop", Crystal Method's "Born too slow", Fuel's "Quarter" and Static X's "The only".
With the underground mode consisting of over 100 races (which doesn't translate into 100 different tracks, since most of them recycle the same courses or are simply set up in reverse), and a quick race option as well as a decent multiplayer option (which is largely irrelevant at this point, since everyone has moved on to different games), NFS Underground offers a good value. With more variety in the racing tracks, the game could've been even more appealing, since repeating the same tracks over and over can feel a bit tedious, but the courses themselves are entertaining enough to make up for this flaw.
NFS Underground is a tremendous arcade racing game, that even when judged against today's standards still fairs very well. It can certainly be frustrating (trust me, I came very close to breaking things while replaying the Market Street course for the umpteenth time), so I recommend taking a deep breath before you venture into one of those marathonic 6 lap races, but putting those issues aside, NFSU is a highly entertaining racer that I recommend to any racing fan as well as anyone that's new to the genre.