Our group is currently using Opium. There's a few things off-hand that I'm missing. Maybe there's a way to do these. If not, please consider them suggestions.
1) I'd like to import Opium KOS list. We've got quite a history built up. I'd hate to leave it behind (and manually converting would be a real PITA).
2) I miss being able to shift-click from the last-seen window to report to other interested parties (that is, shift-click dumps that line to the chat edit box where I can send that text to Party, Raid, Local Defense, Guild, etc.). This also makes (in our case) Opium valuable even when not everyone else is running it.
I haven't toyed with the ability to share KOS entries yet. But it dawns on me an "incoming list" window where you can pick-and-choose lines to add might be interesting. It'll allow you to check the quality of the information. And it'll be a quick place to look for real-time info ("OK - that guy just hit me. Sharing the KOS. Check your incoming."). Of course, I'm sure this feature could also become overwhelmed... and it'd need the ability to import / ignore all options.