How good are the UltraDot red dot sights? They seem to be a well made bargain compared to Aimpoints. Comments?

It depends on what you want to use it for.  A couple years ago, the Ultra Dot was the #1 choice among Bullseye Pistol shooters (it may still be, but I haven't shot a match in a while).  It's a great sight, backed by a lifetime warranty - anything breaks, they fix or replace it.  Although rare, I have talked to people who have used the warranty and it was a no questions asked, here is your new sight kind of deal.

I've got about a half dozen UltraDots on a couple .22's, a .32, a couple .45's and have even used one on a 12ga., all with no problems.  (I've even got one that's still new in the box sitting in the safe - was supposed to go on my backup .32!) The dot is one of the sharpest and most well-defined of any I've seen.  They come with rings, so no extra cost for a mount.  I prefer the 30mm tube to the 1" model.

For a range gun or for IPSC or three-gun it should work great.  I don't use battery powered or electronic devices on a self defense weapon (except the flashlight, and the backup flashlight), so I wouldn't recommend it for that role.  The battery life should be in the same ballpark as an EOTech.  The batteries in my Bullseye guns would last at least a year when I was training once or twice a week and shooting in matches twice a month.

I don't know if it's submersible or waterproof.  I've shot matches in the rain, wind, & snow without a problem.  Unless you are a SEAL, it probably doesn't matter.  For about $125 you really can't go wrong.

Just remember one thing - if you want to shoot accurately with a dot sight of any type, you need to focus on the DOT, just like you would focus on the FRONT SIGHT.  The target is still out of focus.  Most people use optics incorrectly and don't realize why their groups suffer.  Up close & personal, sure you can focus on the target and get decent hits, but to really get the best accuracy, you need to focus on the dot (or front sight, or crosshairs, etc.).  Watching the target is a sure way to turn a 100-10x into a 98-5x or worse!  Been there, watched it happen.  Please note - if you are not a Master or High Master class shooter, you may not notice any difference in group size or may not know what your focus is on when the shot breaks.  If so, try a tritium front sight or paint or scratch the front sight so you have something to focus on.  Then try that same intensity of focus with the dot.  Become one with the dot young Skywalker.