We used to have something like an open roll system on our guild. There were a few exceptions of course, like new people not being able to get items for a given time (or number of raids).
We eventually migrated to EPGP, and we are VERY happy with it. It takes some time to find exactly how to make EPGP work for you. What will you be giving EP for ? What decay ? and so on. It took us almost 2 months to get everything to where it was (plus 2 months of research before we implemented it). But right now, everyone loves the system. Even the new people who come in and have 0 PR. They can see their priority raising fast (because they are not getting loot), and the PR of the people higher on the list dropping fast too. Ok, the gap will still be big for some time, be since they can see the gap closing, it is not a problem for them.
As an officer, I know I'm not the most unbiased person to say this, but I think EPGP was exactly what we needed. Specially with EPGPLootMaster (addon). Loot distribution is so much easier overall.