I've had my ST-i for a few months and use CCDSoft/TSX/PMX successfully with it. I got it for its built-in shutter and it has been great. I bought it 'off the shelf' from Peter Ward in a couple of days so try him with a PM, he may have another?
The only difficulty I have is (so far) I can't find a way of using it with my SX AO-L. CCDSoft wants the SBIG AO to work with the ST-i but I'm going to see what PHD will do with my AO-L, if I ever get a clear sky that doesn't have a huge bright moon in it!
Charles