Well we tested it with about 50 people on the first realm, and about 20 on the "raid Realm", although it did work in concept, it did create problems with the mail system, mail simply stopped being delivered because it was seen as duplicates by the server, and simply got deleted. This happens as soon as you log into either of the realms, after a few minutes (I guess when the server does a periodic data update) a lot of "duplicate error" messages can be seen in console, and then the mail is gone.
We shut down the raid realm after about 3 days because of the mail system conflicts. I would assume this could also happen to items, although none such problems were reported. So like some comments here say, it does work to a limited degree, but there will be problems. I guess it depends on what your needs and expwctations are, whether you do this or not.