I've got an M4 and thought I'd jump in a bit.
I bought the remote and honestly, it's about useless. The instructions that come with it are horrid and all it allows me to do is manually control the direction. Nothing about wall scrubbing or anything. Don't know if the M5 is a different remote or the M4 just doesn't do much...
The turning on the M4 is really finicky, at least with the remote. Seems to be very sensitive to the float position. Make sure that the floats are the same on both sides or will practically turn in circles.
Also, always make sure the handle is at a diagonal. Either the middle two positions or the top/bottom positions. I actually found it stunk when having the handle straight.
As far as climbing the walls, there are two main things: clean the filter and burp it! By that I mean turn it upside down once it's completely in the water to make sure there is no trapped air. The other thing, of course, is to have the right brush. Unfortunately, I don't know what brush I have, but it climbs the walls.
Now, a question for any of the dealer-types out there: Which/how many brushes and filters is the M4 supposed to come with? I know there is a "spring-cleaning" filter, but have no idea if that's what I got or not.