I think depending on the style of wheel they look awesome. Have to be careful that you get some wide enough - you wouldn't want a 19x9 on the rear or they'd look bad.
19's = the perfect size for a non replica wheel. I personally think ccw, tf's or any forged wheel in 18 is a waste of money. The spokes always look way too small due to the huge lip on those type of wheels. 19's look perfect imho.