I got the Zmax v3 mini and then a Zmax v5 telescoping (so I could use the 18650's, should've done that at the beginning but I was bumping up from the eGo so I didn't know any better and hadn't found ECF yet). Both have been great, no issues, everything fit well, looks great and fairly solid. The v5 telescoping has a bit of rock on the extension tube if you don't spin it down tight (and that makes the battery spring go SPROING! when you undo the bottom cap) that's already been noted by others.
I've only been using tanks like the VapeOnly mini BCC, ismoka megatank BCC, Kanger Pro 2 (ack!), Viva Nova, and even the iClear 30s I got with my Innokin VTR rig. All work great on them.
The charger on the v3 kit crapped out after 3 weeks (light stays green without a battery in it even), so I kicked down to buy the 4bay intellicharger i4 (nitecore) which works great with all the batteries I have so far.