8.12 is still relatively new - but there are a number of customers that have already gone live on it. Its still a "handful" right now - and I'm sure that no "LARGE" customer has gone live on 8.12 yet since those implementations take significant time.
What specifically are you looking for ? Just interested in numbers ? Since 8.9, 8.10, 8.11 and 8.12 share the same technical foundation - why specifically look for 8.12 customers ? I'd be interested personally in the number of 8.x customers - and I'm sure the total number is significantly lower than XE and ERP 8.0 users still. However, if you do your research on JDEList - you'll see quite a few upgrades going on, so it won't be like that forever !