I'd get the free Reaper Reaplugs and roll your own out of any piano. Works incredibly slick and can dial in the intensity/range of the effect.
http://www.reaper.fm/reaplugs/ Side chain the dry piano with ReaControlMidi upstream from the processed piano. Alternately, two clone channels of the same piano, one with ReaControlMidi upstream. Change values of the mod wheel to get the exact abount of detune.
This is one of the most useful and unique utility vst's out there. Can be used to honkeytonk or fatten up anything, or just get a pitch shift with no sampling artifacts or latency.
John