I am in a $50 league. I have never used them before, so I tend not to get into any real big money until they are proven to me. I can say the draft went off without a hitch, though the draft itself wasn't setup until a little later than I usually like. Looking at that $1000 league tonight, still needing 7 people in it means you may not even know your pick until 30 minutes before the draft. If the league even fills at all by tonight.
I am not a big fan of the look of the site itself, but I don't base decisions on that. Maybe I am just used to MFL. So far, I have not had any problems, but the season hasn't started yet. If $1000 isn't a lot of money to you, then I don't see any reason not to do it. If you are making that your one big money league, you might consider trying them out with something smaller first and find another big money league somewhere else. Just an opinion, but good luck either way.