I use an Alphatrack and I love it, but mostly for the transport controls. I thought I'd use it for adjusting volumes and automation, but I realised I'm much too obsessive-compulsive for my track volumes to not sit at regular increments. I can't handle looking at a track whose volume is 1.357 dB, for example, and the TV volume has to be on an even number, preferably a multiple of 6.
Don't judge me...
Anyway, the Euphonix MC Mix controller is fantastic IF you're only ever going to be using it on a Mac. There are no Windows drivers and at this rate I doubt there ever will be. The BCF2000 is good value but the faders are not touch-sensitive - if they're reading automation and you try to change them, they'll fight you (unless your DAW intelligently tells them not to). The Mackie Control units are not good value and have a surprisingly high failure rate for a Mackie product.
If you have the ability to try one out, try recording and mixing a complete test song (a cover, or whatever) on a borrowed unit / studio. Make sure it's actually something that will help you (and that amount of money would require it to be pretty damn helpful). I never grew up with analog consoles, I've always just used DAWs, so I don't really have a concept of tactile feedback for audio mixing and don't find a proper control surface to be helpful to me - it would just take up desk space. Make sure it's really something you need, rather than something that makes you go "ooh shiny!".
One other option is an iPad with controller software, which is a cool and novel idea for an external controller you can touch and draw automation with, but with the obvious drawback of no tactile feedback.
