I certainly don't want to go back, and although my recent switch from Glock to HK P30 makes the dot more expensive I'll be sending 3 slides to L&M soon.
After working through the initial learning curve I think the positives definitely outweigh the negatives for me. For close targets, the time to first shot is about the same with the dot as irons for me, but every shot after that is faster with a dot. For further distances the dot wins by so much it isn't even close.
However, I think one advantage that doesn't come up as often as it should is the ability to be target focused. In defensive use being able to clearly see the bad guy and what he is doing, or no longer doing could completely change the outcome of the encounter.
I haven't run into any issues with getting an RMR dirty in normal carry conditions, but I would love to see some options that would allow the optic to be covered while in the holster. I've thought about trying to fab up some type of solution with a Strike Industries Jelly Fish that is tethered to the holster so that it can pop off when you draw, but I have no idea how something like that would work in actual use.