First - there's no reason you have to spend two grand. I went to Home Depot and spent a total of $5.99 for a 12x36 painted shelf board. When I want to stand, I put that on top of a box on my desk, and put my mouse and keyboard on that. Advantage: not only is it cheap, but your setup is portable to any desk that has a monitor arm.
Second - and this is the really important bit - be careful to stand correctly and don't stand too much in the beginning. Build up to it.
What can go wrong? I have personally experienced these two -
1. Don't stand on an uneven surface (like, the padding under the carpet has separated). Less that a half an inch can give you sciatica, which is horrible.
2. DON'T LOCK YOUR KNEES. If you feel yourself getting tired, sit down. You need to keep a micro-bend in your knees, otherwise it's a small but significant hyperextention, which will lead to pain.
Starting out, a kitchen timer might help. Sit for a while, stand for a while. Good luck.