Only if there's no other choice, and it's mainly because I'm paranoid with my vehicles. Even get nervous with my wife driving them. One of my aunts friends owns a valet company and I worked a few events for her during college (mainly Christmas parties for wealthy folks while I was home) and I don't recall any of us doing anything crazy in the cars. I do remember the rear window of a SUV getting busted out, but I wouldn't put all of that on the valet driver. He got in the vehicle and went to park it and didn't know it had a bike rack sticking out on it, so he backed it into the spot as we were to do, and it went through the window of the parked vehicle. The company was insured and took care of it for them. For the most part, it was car people who did the job while they were in school, so they tended to respect the cars.
Also, the 2 best tips I ever made was some old lady in a POS Honda Accord 5-speed who was leaving the Houston Museum's $5k (something crazy like that) per plate dinner/fundraiser ($50), and then a couple of drunk attorneys later that night. When the night was almost over, we drew straws to see who got to stay for the last remaining cars, and I drew the short straw. Since I rode up there with my cousin, he stayed. The very last vehicle was a Navigator and 2 stumbling people (the attorneys) came walking out. HPD stopped them and asked that they get a cab, but the guy was certain he was OK to drive (dude was plowed and so was his wife). I went up to the cop and had her ask if they wanted me to drive them home in their car and my cousin just follows me there, and they were OK with that. Dropped them off at their River Oaks mansion and they gave me $100 tip. When I got into my cousin's car, he asked if they tipped, and I said "yeah, they gave me $40, here's your $20."