To my knowledge, there are 2 grips now available, and one more not yet available. The grip options from our own John Milich (username jlm) is available in addition to the official Olympus HLD-6. The offering from Really Right Stuff isn't shipping yet.
Can you show us your OMD with grip attached, plus any comments? My preference has always been to avoid making my camera any bigger or heavier, but on a camera this small, my mind remains open.
Even if you don't have a pic to show, tell us why you do or do not prefer to use either grip.