My ex-wife puts knives in the dishwasher, and hers are always blunt. Mind you, they're crap knives to start with. The other problem is that the knife is always in the dishwasher when you need it.
I've never used a sharpener - the grinding noise as you drag the blade through it sounds too much like damage happening. For the past couple of years I've been using a ceramic "steel" , and I find it much more effective than the steel steel I used before. When I bought my insanely expensive Global knife, I couldn't persuade myself to get an £80 Global ceramic steel as well. I subsequently found a ceramic steel in Ikea, for £10 IIRC. Actually, the top-of-the-range knives I bought in Ikea are pretty good, too, and much cheaper than Global.
@Hungry Sean: "Sabatier" isn't a brand. It used to be a name used indiscriminately by manufacturers in Thiers , the French equivalent of Sheffield, but more recently it just describes any French-style cooking knife, typically with a triangular blade and a black handle.