I had an engine failure in my 24' Zodiac Hurricane in deep water about 600 miles south of Hawaii, and used a sea anchor overnight while I got some sleep. Seas were about 15' with a 20-25 knot wind, and only a slight current.
I used a 9' Para Tech sea anchor with a 15' length of chain mid catenary (a great help) and trip line with float for recovery. It's the only time I've deployed one except for testing, so I had (and have) very limited experience and am certainly not an authority.
I found it deployed easily over the side and "caught" and as soon as some pressure was taken on the line, immediately bringing the bow into the weather. I payed out the line about 200' and tied it off. It felt exactly like dropping anchor, and held out position with minimal drift. The angle of the anchor rode is more horizontal than when using ground takle, so burying the bow was not a problem.
Recovery was a bit tricky because it was impossible to haul in the line, which essentially means pulling the boat toward the sea anchor against the prevailing weather. It's handled just as if you were anchored to the bottom, powering forward while simultaneously taking in the line so it doesn't foul the prop. It took a while, and I wouldn't like to do it often in heavier weather or without a trip line, but I was able to bring it in without complications.
This web site has good information on the subject http://www.seaanchor.com/.