The only "disadvantage" that I can think of (that could potentially affect a single pedal player), would be how far away the hi hat is gonna be.
Now, its not too far, usually. But almost every double pedal setup that I've seen, puts the hi hat a lil further left. I don't see it as an issue, as I'd rather have the extra kick pedal there, but someone who doesn't want the extra kick, may find it further than they prefer.
Other than that, if you don't look down, you would never even notice there's a double pedal.
If it's your kit, and you want the double..then do it. I'm sure single players will still play just fine... but try to get double kick action out of a single pedal..