This comes up often and I often end up being the only guy that thinks a cover is invaluable! I hear all the same usual cons - too hard to take off and on. Scratches the paint. A good wax job will protect just as much. They just rip in six months and are not worth it.
My thoughts on the four most common complaints:
1 - Its a lot of work! Yes, it is some work putting them on and taking them off(our coach measures 43'). About 45 minutes to put on and 20 to take off and roll up to leave on the RV pad. I can put in on in 30 minutes if I can talk my wife into helping :-)
2 - It'll scratch your paint. I have been using a cover for almost 7 years now with zero harm to my paint or gel coat(on my previous DP). The exterior of my current and previous coach look like new.
3 - Just wax it! Perhaps in some climates. Not a chance in a climate such as AZ. Years of exposure to our brutal sun and your paint, gelcoat, decals..whatever, don't stand a chance. Even with the best wax out there. Drive through any storage lot here in AZ and see how that wax theory works. Again, this may be unique to climates that are as harsh as AZ.
4 - They just rip after one season. Mine have always lasted about 2 1/2 years. The cover itself doesn't rip but the straps dry rot and fall apart. I always pay the extra $$ for the three year warranty and just get a new one for free and then buy the warranty again. Now...I AM careful when installing it to not catch any sharp corners and I also cover a few sharp corners with tennis balls. We are in the middle of monsoon season here and the cover still holds up just fine.
Speaking of covers, this reminded me that it is time to go trade in my boat cover for the same reason...the straps are shot.