As long as they are setup correctly, and the users arent holding really long conversations, it works well.
We had on for our EMA last year, on a 250 tower!
I would recommend having different PLs on the tx/and rx channels, so that the others listening dont hear you talk, and then hear you talk again through the repeater. This would also have the benefit of having a "talk around" channel that did not have the PL needed to get into the repeater, if you were close enough to the other person not to need the repeater.
Steven