I don't usually find suitcases to be the problem with taking up too much space in the overhead bins, the biggest problem is all the bloody small bags/jackets/laptop bags/random crap pax seem to enjoy stuffing overhead!
Personally when I travel as a passenger, I prefer placing my handbag and jacket under the seat infront of me, no chance someone will steal it or pick it up accidentally, plus I generally find the floor space a damn sight cleaner than the bins!