Okay, so it's been a while... But I finally have a light and a little bit of experience training with it.
I ended up with a third generation Inforce APL (the full size light). I have had it mounted to my PX4 since February (I bought the light from a Black Friday sale, so that was some pretty fast shipping ) and since that time I've fired... well, less rounds with it than what Gabe White probably uses as a warm-up. About 400. What can I say, due to time and money constraints my volume of shooting is pretty pedestrian by P-F standards.
Right off the bat there was a bit of an issue; while the APL otherwise fits the Beretta just fine, the trigger guard blocks the paddles of the light from moving far enough. I fixed that by some judicious whittling of the tops of the paddles.
Once I got past that issue, I must say I like this light. Having small hands, no weapon mounted light is really easy to use, but I manage with the APL with definitely less trouble than a TLR. Two-handed, I am able to engage momentary on with little issue and minimal compromise to my support hand grip by moving my support hand index finger to the front of the trigger guard and working the paddle with the side of my finger. (This is pretty much how I've used the TLR, as well.) One-handed, the only method I've come up with that works reliably enough is bracing the butt of the pistol against my rib cage, kind of like some folks teach retention shooting, and activating constant on with my middle finger. With a bit of practice this is pretty workable and I can do it regardless of which hand I have the pistol in. One-handed activation was something I was totally unable to do with the TLR, so this is a clear improvement.
Size-wise, the light is the same width as the pistol, which is nice. The bezel extends slightly beyond the muzzle. Carrying the pistol-light combination in an IWB holster (JMCK IWB3 with 25 degrees of cant), the light does create a small bulge to the butt of my trousers which needs to be covered by the concealment garment, but at least it is doable. Duty holster wise, I was able to make a Safariland 6005 work by cranking down on the lower retention screw.
The 400 lumen beam has been sufficient in all the training I've done with the light thus far. I must say, in retrospect, less lumens would have been a handicap. I'm glad I got a light that is powerful enough to be useful.