Delay can sound very effective on vocals with or without reverb though I think you always need a touch of reverb just to take the dryness off your vocal. But the only thing you must be careful of when using delay is that if it is a longer delay it MUST be in time with the tempo of the song you are using it with. With the band I play in we can't keep changing the delay time from song to song so we only use a VERY short slap back delay that doesn't conflict with the tempo of any of our songs. Sure it's a different effect but we found that long delays would cross the tempo of most of the songs and would sound messy and unmusical.

Of course in the studio you can customize the tempo of the delay from song to song very easily. Or in a MIDI setup if the delay time can be synced to MIDI clock then it will automatically change with the MIDI clock timing.