Everyone has their opinion on using lasers, it's been hashed out many times before on this forum. Many do and don't like them for all the reasons stated in this thread and others (do a search for crimson trace). If it works for you, go for it. I don't like them for the reasons I stated.
As for changing my grip, thats fine for the range, but in a shooting for my life situation I would rather not have to worry about my thumbs getting in the way. On a sub compact, when using a correct two handed grip there is not a lot of room to be moving the thumbs around. I also would rather not have to worry if its too bright outside to see the little red dot. I want something on my gun that is effective 100% of the time, and thats a set of good night sights.
As for holsters, yes there are plenty of lefty holsters that will work with the CT, there are many that won't. The ones that won't work were designed to have the laser emitter on the outside (right side) of the holster (away from the body). They make the lefty holster a mirror image of a right handed holster, with the cutout for the CT on the outside (left side) of the holster. Too bad you can't move the emitter, it's still stuck on the right side of the gun between the gun and you which is were the belt slide or paddle attaches to the holster. I have a left hand Blackhawk Serpa and a Safariland model 6377 that I can't use with the CT.
For some a laser works very well, if it does, more power to ya and happy shooting. For others it's not the perfect solution and they would rather not use them. Lefties are presented with a few problems they need to keep in mind if choosing the CT.