I bought the cheap stuff on ebay (it is the same material as the name brands, just not a name brand) and installed it myself on my 03 corvette, and after that I vowed I would never fail to put it on a car again. It protects from rock chips and makes the bugs wipe off very easily.
As for noticablility, I've put it on a red, black, and white car, and it is most noticable on my white diamond CTS. On the other two cars, no one could tell it was on there until I mentioned it to them. In fact, my dad is super meticulous with cars and actually got mad because he thought I scratched my vette, until I told him it was the clear bra seam. It is really only noticable when part of a body panel is covered and the rest is not. Like the hood piece. You can't tell anything at all on the bumper or headlights. On the white car, it is a little more noticable because I think it messes up the way the light interacts with the tri-coat paint and gives it a slightly darker hue, but I still have to tell people it is on there. I spent about $60 and 3-4 hours to cover my front bumper, hood, fenders, headlights, A-pillars and the first 4" or so of the roof (the leading edge that is exposed). I also bought a couple feet of uncut material to make my own pieces for the rocker panels.
For ease of removal, I took it off the driver's side mirror when I sold the red car to redo it where I messed it up during install, and it came right off with a steady pull. The best part is I can replace it 10 times and still spend less than the more expensive stuff. I can honestly say every person I know that cares about their car and has seen it on mine has wanted it.