There are no roll-up screens that are really 'good' in my experience. They all develop waves.
So, unless you are prepared to invest in a good tab-tensioned screen, or need something for the office, why not get a cheap manual roll up screen and save a couple hundred bucks towards that good screen - or for a decent DVD player or speaker upgrade?
The BEST way to do screens really is fixed on wall.
The second best way is tab-tensioned electric. (or manual)
The next worse is manual screens
Finally the worst are electric screens that aren't tab-tensioned. They are no better than manual pull down screens - but they cost more. What a waste.