BPM Studio essentially lets you mix MP3s (and other sound files) on your computer, like DJs mix vinyl on turntables (or of course CDs). It can also be bought with an external controller, which I have not used, but from the website it looks like a CD controller. However, this external controller adds cost to the system.

In use BPM Studio is quite easy to grasp. Loading it up first time, it searches your hard disk and puts them in the MP3 database. Just drag and drop tracks onto the player. Studio then detects the BPM and you can start playing. Unlike other players you can change the speed of the tracks without affecting pitch, just like on expensive CD players. I have to say the tempo control is very impressive, and sounds great. There are other unique features too, such as the built-in sampler, and ability to write your mixes directly to CD (and rip them too if you want). The samples can be triggered by pressing a hotkey.

Despite having all these features, Traktor by Native Instruments is better. With BPM Studio you do not have such good control of the positioning of the track. With Traktor the track is graphically displayed and you can drag it into place (just like vinyl). I would say BPM Studio is probably best for those who like CD mixing, whilst Traktor suits vinyl mixers better (ie. most DJs). Also you do not have helper functions like lights, which are triggered at every beat and beat offset indicators. Having these helper functions in great, as it lets you focus on doing more creative mixes (having freed up time from beatmatching). In addition the equaliser on Traktor is easier to use (and has a nice filter). But to decide between the two I would recommend downloading demos of the two. I'll stick to Traktor for most of the time, but will still keep BPM for those cool features like the sampler and tempo control!