In High School we rotated the DM between about 3 of us. With one guy particualrly the DM. In Uni, I played and DMed as there were no shortage of games, but since then, in the last 10 years I have been a player more often.
I prefer to play as I have yet to take over any fantasy world I have played in lol (joke).
In the last 2 years, however, I have been a player 3 times and a DM twice including currently DMing a game and playing in another.
I am new to Pathfinder, having bought the books about 3 months ago and was new to D&D 3.5 when I picked it up late last year (the last time I played a long game of D&D was AD&D!). So I joined a game as a player so I could learn the rules quicker (I have read the rule book, but find I learn quicker if I put the rules into practice.) and learn how to play a class my party does not play or I have not played before. I picked a spell caster for this one, as it is handy knowing spells as a DM.
I am torn between whether I like DMing or playing better. I was offered to be a player in the game I DM when we converted to Pathfinder from 3.5 but knocked it back. I love building the world, drawing maps and all that.
I am still rusty as a DM, I was a good one back in the day (Well, so my friends told me), so I am slowly getting back into form. :) But no matter what I do, rpging is still the best!