I've got a Para OPS, which is Officer sized, and it runs great. The single stack Paras are very reliable. Also, I had a Colt Lightweight Defender, and it was almost unusable. The aluminum frame made it so light as to be impossible to use due to recoil with normal self defense ammo. I think it was just a bad idea to make that pistol, and the new colt looks worrisome too. If you want something small, it should have some weight to it, this "lightweight" aluminum frame thing is worrisome. My Para is stainless, so it takes up the recoil nicely, doesn't kill your hand. Not to mention it has slim grips, unlike the defender which came with these fat fat grips that made it useless for concealed carry, my XD is thinner with a double stack magazine!
Anyway, just because it is Colt doesn't mean it is good. It might be, but it might not be. Also, they still haven't figured out that maybe beaver tails and extended thumb safeties and such are kind of nice to have, perhaps they should upgrade a little.
Outside of the lack of beavertail the gun has been soundly praised so far.
Like anything else, only time will tell if it is a good gun in the long run. This is
not a Defender and you shouldn't even try to make a comparison to that gun.
Any individual gun might be reliable and might not be reliable. Recently Goose
posted his travails regarding Para-Ordinance yet there are numerous posts
from satisfied owners of these same or similar pistols. Your experience with
the Defender is probably not what every owner had (I don't know much, if
anything, regarding the history of Defender pistols) and, in fact, around the
Colt owning fraternity they seem to be a very sought after pistol.
Your observation of small vs weight is exactly why it has an aluminum frame:
Weight, and lack of. I have a steel officer's model and it is a great pistol but
light it isn't when loaded. Weight is why they make alloy, aluminum, and
Tupperware components for guns. Are they as tough as steel? No. Will
they do the job. I expect so. YMMV.
As far as using self defense ammo. I also have a Lightweight Officer's Model
(alloy frame) and it is a extremely nice gun to shoot and control, regardless
of ammo. In fact both the Lightweight and Standard Officer's shoot similarly
and are very comfortable to shoot.