I have carried the x300 with the switch for several years. Having been on an entry team on several hundred warrant entries, I have used the light extensively. This is one of the best tools I carry on the job. You can gp and talk on the radio at the same time. Searching is much safer given proper muzzle and trigger disciplines.
I strongly caution you to maintain a strong master grip, not repositioning your hand. Several tac-teams have had negligent discharges due to the fact the operator repositioned his hand, loosing the master grip. This resulted in the #2 finger ending up inside the trigger guard. They apply #2 finger pressure to activate the light and bang. If you train properly, you should not have issues.
The problem I see without the DG switch comes when you need a target illuminated and rounds fired. With single handed shooting, the light has to turn off to fire (assuming there is not time to activate the steady on mode).
Just my two cents...I hope it helps. Money well spent!!!