http://icrontic.com/article/the-real-difference-between-workstation-and-desktop-gpus
Drivers, support, stability.
http://forums.cgsociety.org/archive/index.php/t-808900.html
Again, performance not an issue, its all about stability and support.
Put it this way - if I buy a Quadro, I'm not buying a Fermi Quadro. THe prices are stupidly high. I could buy a FirePro, which are cheaper, but I'm worried about compatibility. I know Nvidia's driver support has historically been better for professionals. If I buy a GeForce, performance WILL be better, no question. Stability may or may not be an issue. Its a gamble that a lot of people seem to take, and they seem to win. In other words, a lot of people use consumer level cards with no problems.
Heck, its a small business, budget just does not allow for an $800 card. Sorry, it just doesnt.