I recommend you examine the features you need, the ones you want, and the ones that would be 'nice to have' or you expect to grow into in the near future.
Look at your work flow and then start looking for a product that has the features you want/need and works best with your work flow.
For example:
If you are comfortable with a DAW setup, then something like MixMeister Fusion could be a good solution. But if you prefer the Deck A/Deck B approach to DJ'ing then it's a very poor choice.
There are PLENTY of other options.
Serato Scratch Live/Serato Itch - but it doesn't have any function to 'beatmatch' the tracks. For some, not an issue, for others, a major shortcoming. There are other issues - including the inability to use any other sound card besides the SL1/SL3/TTM57SL/etc. A lot of people tout it's stability, but I had 3 crashes in 6 months - which is why I stopped using it (BTW, on 3 different computers, including 1 on a friend of mine's computer who used Serato exclusively). The point is that there aren't any solutions that are 'perfect'. You have to prepare accordingly... I've even seen video of CDJ's being swapped out during an event.
Torq/Torq LE - A nice product but because of a reorganization, and a variety of other challenges, the updates have been slow in coming lately. I've used it extensively with both external control and with midi - using sound cards from a variety of different companies. I've found it to be quite stable and one of the most feature rich products on the market.
Traktor - Another nice setup, and I've been using the Traktor LE product with a Stanton SCS System 3 rig. It's a nice product and integrates well with the System 3. It has limitations, but that's a limitation of this particular version of the software. The Duo and Traktor Scratch versions have more features.
MixVibes - It's out there but I haven't use it.
RockIt - Haven't used it.
OTSAV - Haven't used it, but know a number of people that do, and love it.
BPM Studio - Haven't used it, but know a couple people that have used it in the past or still do.
MixMeister Fusion - I originally got Studio to do some remixes (long story) and it worked flawlessly for this purpose. I started playing around with Fusion and found that the work flow is very similar to using a DAW. It's a nice product, but in all honesty, I feel 'out of touch' when using it. I don't feel like I can affect the music 'stream' live. I've considered adding the MIDI controller for it, and still may - but it's a GREAT product for doing expanded intro's and the like because you can set up the playlist using a pause as the transition and rearrange if you have to on the fly. All in all, not a bad product - it just takes a little getting used to.
Virtual DJ - Havne't used it.
MP3 Tunes V2 - Free product - if you can still find it that runs on almost any hardware (it runs on a Pentium 233MHz machine with 64MB of ram with Windows 95!). It's feature rich for a free product and was designed for use with internet radio stations - which means it has shoutcasting/icecasting/etc built right into the software. It has the ability to do drops and a lot more - but no midi control is offered and the updates won't be happening any time soon (development is basically dead). I've used this for a 'backup' solution and it was one of the first products I ever used for computer based DJ'ing. I still recommend it as a 'starting' point for those just considering the move to a computer based product.
MegaSeg - a Mac only product, and based on my original research, the only one that will play DRM tracks from Apple (iTunes). While not a problem any more, it was at one time. It's one of those products that people either love or hate.
The list goes on and on.... LOTS of products... LOTS of solutions.... LOTS of ways they work. The problem is finding the one that works best for YOU.