All my normal gear is Surefire. Recently I put together my first AR-15 build from spare parts and made it themed in lightweight and inexpensive. I had a couple of TACM-III setups I got cheap as a C3 dealer at a gunshow. Didn't know anything about them, forgot about them, but resurrected them when looking for spare parts. It was some years ago so I thought they had gone out of business and I was lucky to have spare lamps. They are still here, and I was pleased. They are bright, and very lightweight as they are machined Delrin. I am using the standard cap (on-off-momentary). I have not used the pressure switch yet. The rail mount looks bulky, and the ring knob looks very snaggish, plus retail is about $74 for just the mount! (from TACM3). The handguard mount, simple and effective, is somewhat dated looking, held on by one machine screw, and far more expensive than I thought it should be ($50), but it works. The system itself was designed for weapons so it should be recoil worthy (I hope). You seem to have found better prices.
Since I already had them, it worked out great. However, one could just buy a nitrolon ($28)with shock isolated head ($20) if you want a surefire version, thought the pressure switch is expensive ($72) though you can get a cheaper non-SF switch ($25), then there is a mount ($20). Here is my TACM-III, with the rest of the cheap lightweight plastic gear (First Samco Fobus Handguard and FS2 Light mount).
[img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=17021[/img]
I don't know if I'll ever use the pressure pad switch. In this configuration, I just rock my knuckle forward for momentary on. It's not the switch they offer now, it's a flat totally deltrin knob without the button in the middle. I haven't got to shoot with it much yet. Hope the old tailcap and pressure pad switch holds up...