For me, I use them alot, they are great for walk around situations in my opinion. I wouldn't recommend using them for routines unless you are comfortable palming cards away and getting burned by spectators wanting to see the deck afterward. I use them if I am approaching a few people sitting around. Perform the routine and then I can walk away without them really burning me too much. I do agree with the above statement, if you want to get Gaffs I would go with the Ultra's, because the DVD's you can get with them provide more variation for all the cards you have. With the normal gaffs what I find is that maybe only 6 tricks (I think) are covered with the cards, so you are left with some experimenting and innovation with the original gaffs.
One thing also about the gaffs, is they are no Dresscode, they aren't headlinging tricks, they are used more to fill in for tricks if you do a routine with them, and some of them are more to get a laugh from your audience than to actually blow their minds. Hope that helps Cheers!