Just an update as this thread as lurched around a bit
I tried The Sigma 530DG today together with AlienBee 800. It worked great triggering the AlienBee 800 every time. It was nice to loose the cord and go wireless too, especially on my rebel which requires an adapter to use the cord.
Also this may sound silly to some that i forgot, but with so much light available do not forget to drop the iso 100 or 200. My Camera usually sits at 400 unless I am outdoors and remember to lower it because with out extra lighting of course its needed.
The light sources were so powerful I was virtually forced to remember to cut the iso as I did want to keep bumping the F stop, I had stopped @ F 7.1 before I remembered (shutter speed was 1/200 [max sync though I have previously found I can push to about 1/320]). With the change to ISO 100 I was able to up the power to 1/16 and about 1/16 on the Alien Bee with shoot through umbrella. The flash was pointed at a near by wall to bounce (before the change in ISO they were at 1/128 and 1/32 power respectively, the min.).