It won't hurt if you have to thin it with a little water to get it to spray well. All these guns are going to be limited for most applications over a bigger airless rig, but for the average homeowner that isn't going to get into too much, they are fairly nice. As far as the vertical spraying thing, anything with a pickup tube at the bottom of the cup will suffer. Just keep the cup filled and spray up at an angle, not straight over your head. Spraying the bottoms of walls will not be a problem. Another thing to look at is the ability to repack them and the price of parts. If they can't be repacked, they are disposable then. The first round of Truecoats couldn't be repacked. The next Gen could be repacked twice. Not sure if now they can be done more than that or not. If you can do it twice, I would imagine you could repack it more then. the ability to switch tips is important also if you want to be able to run a variety of materials through it also. You'd want a different tip for spraying a wall than spraying a deck for instance.