I've a v3.1 but not sure there are enough features on the Gen 4 worth the upgrade. If I were going larger volume then the 65ltr version would be a no brainer but see little reason to replace with a similar sized similar system. As it happens I have just built a larger capacity system, but went 3 vessel route...far cheaper. Since people are clamouring for the plethora of all in one systems hitting the market at the moment at all price points the value of used 3v compoenents are dirt cheap so I picked up a complete 100ltre capable SS brewtech and Blichman set up including chillers, control system and everything apart from fermenter cheaper than a 65 litre Gen 4. So if you have the space and inclination to build up your own 3 vessel system it might be a cost effective route.