We just started using ICSSync with Zimbra 7 and it works in both directions. It also works with unsigned SSL certs which was important for us.
I tried it before LVSync because we can use it for 20 days before buying it. If it continues to work well, we'll most likely buy it. Has anyone else used LVSync and had success? I'm interested in it but there were some bad reviews (for what little that's worth). I just wish I could try it out first, because if it works as advertised it's a better choice than the ICSSync.