It seems a lot shorter than the original, but then again, the original wasn't as pretty, and didn't make as much sense.
I'll get this out of the way now: the controls could've been better. They felt tighter in Legend, and most of the puzzles could have sacrificed physics complexity for accesibility. Also, even though some features weren't in the original, they could have been handy this time around, such as binoculars (minus the cheesy R.A.D. mode from Legend) or grenades. After getting a hang of the controls, you can actually pull of some pretty impressive flips, and if you're up to it (or are playing the Time Trial modes) you can get through long sets of obstacles with only a few button presses - that is, if you've mastered the very loose controls that will torture you the first run through.
The graphics are amazing for being on a last-gen system. Everyone still realizes the PS2 has some gas left in it, so why not blow out the engine? That's what CD did. They pushed the system to the limits with lighting, models, and awesomeness. A lot of the time, you have to stop and look around to appreciate how much detail went into the world. They broke the limit of what the PS2 can do, and it's worth every byte.
The sound is also amazing, bringing back the original sounds re-recorded for the cool kids of today. The ambience makes the game feel like it did in 1996, with the sense that you're alone and isolated in the giant tombs. You also get that rush when enemies jump at you, and the music starts up loud - you know, the "HOLY CRAP" feeling where you pound on the controller and jump from your seat. The sounds still jump at you like they did before.
They did a good job of recreating the original levels, but it still feels a lot shorter than the original - longer than Legend, but shorter than Metal Gear Solid 3. Having Time Trials makes it seem even shorter, because when you go back to a level you have very little extra time to do anything else - so if you fall, you'll probably fail. It's got some goodies like Legend did, with different artifacts and outfits (including the original 3D model from the first game [sweet!]), but nothing really holds your attention after you beat it.
All in all, I'd say it's definitely a game to have on your shelves. It holds up as a great Tomb Raider game, and stands alone nicely apart from the name. Even though it has its controller issues, and the replay value leaves some to be desired, Tomb Raider Anniversary is one to get.