I like to play 2v2s, 3v3s, 4v4s with friends, and I also like doing random ones as well. I've noticed a pretty even divide between people who like unit control, and people who don't so I thought I'd poll Reddit.
Some people swear by it, even to the point of sharing unit control the second after sending their workers to mine.
Personally, I do not use unit control. I feel that if you have 2 players of different skill levels, the weaker player gets carried along and really only ends up building his base and maybe scouting, and the second player has an army twice the size that he micros in order to beat up on an even-matched team of 2 non-shared unit control players. When I'm the weaker player I just feel so bored in games with shared control, because either I let someone else do the micro, or we end up tussling and mis-controlling our army by trying to move it in 2 different directions.