How long of a trial are you thinking of? If it's a significant amount of time, I think this could be hard to do from the perspective of the candidate.
If I'm currently employed, there's probably no way I'm going to quit my job for a month-long paid trial period somewhere else. If it didn't work out, I'd find myself without a job and would be forced to take a hopefully short sabbatical for more interviews (and this wouldn't be possible at all for people who haven't saved up enough money to do so). It just seems too risky.
If it were longer, say six months, I might consider it, but I'd expect a decision to be made well before the end of the sixth month--that way if you didn't want to hire me full-time I'd have time to talk to other companies before losing my income. Even with this concession, I'd have to want to work for your company an abnormal amount to do this, though.
Perhaps a happy medium is a take-home project taking one or two weeks of part-time work, paid for at market wage.