Just an FYI, for those who dont have the experience with them.
Sure, you would prefer the glass were clean and clear, but the dot still works fine if it isn't. In fact, you can cover the front of the sight completely with a piece of tape, and if you're using it properly, ie, shooting with both eyes open, just like you do with the irons, the dot will be there and you can still shoot as you normally would. You don't have to see through the window for this to work. Works just like your long guns with the front cover closed.
Just like the irons, crap does get into/onto things and the dots are no different. And just like the irons, if you keep up on things and maintain your stuff, it doesn't have to build up and maybe become an issue.
As Ive already said, battery life isn't an issue if you're paying attention. And even if you arent, you still have your backup irons, should you need them. As with most things, paying attention is better.
I just gave the water drop thing a go. There was a little bit of distortion with the water on there, but it was gone with a quick shake, and about as debilitating as a drop of water in the rear notch of your irons, which is also gone with a quick shake.
Ive also been shooting in a light rain with mine in normal practice, and never encountered this happening either. There were water drops on the front of the screen, but the hood seems to cover things well enough when it comes to the projector. When I just tried it, I had to hold the gun upright and reach in and place the drop on it when I did. Could it happen? Sure. But it doesn't seem to be something you need to dwell on.
Ive heard all sorts of stories about screws coming loose, shearng off, sights coming off, etc. I have eight guns with dot sights now, and installed every one myself, using a torque driver to set the screws to spec. So far, Ive had good results. The only problem Ive had, has been one screw coming loose, which I retorqued and hasn't been an issue since. If you can follow directions, pay attention to your stuff, and maintain it, I don't see this being an issue.
As far as brightness goes, you have a couple of choices. A number of sights self-adjust to differing light. Some do it pretty well, some not as much, and things continue to improve as well. Holosun's new SCS models do it a lot better than their earlier sights. Ive been told the Trijicons do it well too.
Ive been using one of their Holosun's 407c's for over a year now, and while it does have a self adjusting feature, it doesn't work as well as the SCS. I found I liked it better just locking the auto adjust out and setting the dot to a brightness I can see well outdoors, and go with that. At bedtime, I hit the gun with an air can to knock off the dust bunnies, and drop the dots brightness down two clicks. In the morning, I bump it back up. Other than that, there's no need to touch it again.
Anytime you switch over to or try out new things, there's always going to be a learning curve. How things go for you usually depends on whether or not you're open to learning it or are fighting it. The more you fight it, the harder it usually is. I would say here, if you know or can find someone who has been using a dot sight on their gun and has things figured out, it would be well worth talking to them and getting some pointers.
Changing up your presentations a little, and knowing where your eye will pick up the dot quicker, makes a big difference in how things go. And if you're a point shooter, who is accustomed to, and comfortable with shooting over top of the gun, I think this will be a lot easier for you, as you're already most of the way there.
I also think you're going to find that your iron sight shooting will improve and sharpen, too, as all of a sudden, your irons will be aligned on presentation, without thought or effort on your part.
), etc, etc. Things would be so much easier! NOT! 
Regardless, it pays to constantly check them, especially the taller suppressor type.
