Depends what it's for. If you're planning on becoming a hip hop producer, they're pretty cool, although you'd do just as well or better with some software and an m-audio 4x4 pad.
http://www.m-audio...erFinger-main.html It's a quarter of the price of a used mpc 2000, way more flexible if you're already rocking a laptop.
If you just want to dick around with some hardware, I picked up a Roland sp 606 for $250 on craigslist - it's all the fun of the akai, with a cheaper build and way more effects. Mostly I use it just to trigger samples when playing with the band, but it's fun for random chopping of drum breaks and building a virtual drum kit without having to fire up the computer. It also beats the hell out of my old Dr. Rhythm for recording demos of rock songs, I bash out beats 'live' into the multi track and don't bother with programming any more.
Check reviews and info online, there's a ton of people using the mpc on futureproducers.com, some quality reviews at soundonsound.com, and videos of DJ Shadow playing the drum and organ solos in 'Organ Donor' live with an mpc on youtube.
