Clumsy interface, support does not respond (even after purchasing a subscription). It messed up my contacts list; I found duplicates, missing contacts, some contacts in their respective label/group, but missing from "My Contacts" and vice versa. More importantly, I have little to no confidence that my contacts will be successfully synced and shared and not be seemingly deleted at random.
You can get a free trial, so go ahead and try it and see if it works for you. Be sure to completely backup your contacts before trying it, just in case it messes it up. Yes, Shared Groups is cheaper than the competition, but it is not worth the headache.