I've somehow managed to get my entire guild to update omen to the live wowace version for the past 3 raid days, since we started work on reliquary in BT.
The last full sync was last night getting everyone on 68490.
Its been working fairly well (i.e. all versions since the last network protocol version rev).
The only odd problem is that sometimes a tank or two stops updating for specific mobs. Generally its all mobs for any given trash pull, or half the mobs in a hyjal pack. Each pull of Bloodboil would be fairly unpredictable if a tank would be in omen or not.
Definitely odd, but not a absolutely massive problem since we did manage to down bloodboil on our first night even with omen acting a bit odd :)