I avoid them. If you walk in the slightest breeze or if you walk to fast, it will blow your coat open and expose it. Most will let the gun swing away from your body if you bend over too. The weight on your shoulders really blows too, even when balanced out.
They are extremely fast though, so long as your coat is unbuttoned. Keeping the muzzle to the deck upon the draw works well, except most don't do it. Strong side is much better IMO in most situations.
In the summer, I wear either a wife-beater or a body tight Heatgear T-shirt. I then put an over shirt that buttons up over it. I buy these shirts a little bigger then normal so it covers the bottom of my OWB holster.
In the winter, I wear a regular t-shirt or long sleave shirt tucked in. I then have a leather jacket that covers the base of my holster. I had it specially made by Coronado Leather. Top notch stuff if you like leather that isn't a biker looking jacket. If you want a biker style, go Langlitz.
The only problem that arises is when you wish to remove the jacket. Like in the restaurant. Usually, I take the jacket off my arms, and let it fall behind me, still covering my sides. IWB would help so you could just untuck the shirt and leave it loose, but I can't stand IWB. They put my ass to sleep -- yes, even Milt Sparks. I have low body fat %.
Best bet is to leave the jacket on when possible. I built mine so it breathes extremely well. It is a cool jacket for weighing about 5 pounds.
I never have to wear a suit, so I can't comment on that aspect.
-Steve