Better than the E-series...I carry the XD-s with Viridian's Reactor R5 ECR (Extra Combat Readiness) instant-on laser. No button to hit. Mounts to the rail just like the E-series. Has a magnetic on/off switch. My Alien holster is made for this combination, and has a magnet button built into the kydex.
When the magnet is next to the laser, it turns off.
When there is no magnet next to the laser, it turns on. In other words...draw, and it lights on its own. By the time the muzzle clears my holster, the laser is on. No thought required.
Draw.
Place dot.
Pull trigger.
Make hole(s).
The R5 can be had either in green (mine), or red. You can set it for steady-on, or flashing. My green is VERY visible even in full daylight. I've checked it through my patio door (glass), across the patio, across the driveway, and onto my garage stone wall. 40 yards, full daylight...totally visible. I run it on flashing - more battery life (I change them once a year; my first set went two years before dying), and it jumps out more to my old eyes. And, if it doesn't light (which is why I change it in half the time it takes it to die)...I have my TruGlo tritium sights.