Ditto on SGAmmo. You may be able to find slightly better prices elsewhere, but I trust SGAmmo and would rather pay a little more to them. Still a LOT cheaper than local!
My wife has the Deltapoint on hers and loves it. I have the Trijicon RMR on mine and love it. The only problem I have with the Deltapoint is finding them.
My wife's 22c was doing the same. We contacted S&W, they said to send it back and they replaced the rear sight. She's had it out to the range twice since getting it back, and so far it's been fine.
Put me in the 9c camp. I have both, and routinely carry the 9c (though I've been carrying my 45c the last couple days). I like the shield, and carry it occasionally as a pocket gun, but much prefer the 9c for IWB carry.
I'll agree with those saying go for it. I've got the 4.25" 9mm and the 5" .40. Great triggers on both. Right now only one has an optic (currently on the 4.25", but was on the 5"). My wife has the 3.5 MOA Delta Point on her CORE, the dot's too small for me so I went with the 6 MOA Trijicon.
Congratulations! I've long regretted selling the 6" 629 I had many, many years ago, and yesterday picked up a 4". Looking forward to getting it out to the range today.
My wife has the Deltapoint 3 MOA and loves it. I went with the Trijicon RM08 and love it (in fact, I'll be ordering another in the next week or so). We haven't tried any of the less expensive optics, sorry I can't recommend anything there.