yes
well, not a full suit, but with my 3mm jacket (long sleeves and short legs)
but that's one thing I like about the Farmer John style...the front sipper makes venting it very easy.
OK, everyone is different I guess. I was just wearing a 5+5mm (i.e. 10mm on torso) farmer john style suit in 29 degree C water and wasn't too hot. I don't think any ocean gets any warmer than that at depth. I can't remember the last SCUBA dive I did in a 3mm suit, but I wouldn't have been very happy!