I replaced the stock electronics on my Mk15 with a Hammerhead Rev C. I really like it.
Positives:
- it holds set point really well
- the solenoids are great. In about 15 years of use I've never had one fail.
- the DIVA hud is fantastic. I have mine set to simple green/good, red/bad, amber/something changing. The vibrating alarm though is its real strength. It is almost painful, you physically cannot stay on the loop for very long with it rattling your teeth. I've upgraded to the new version and the vibration is even stronger.
- plenty of scope to customise the settings. To be honest, I set the setpoint and I've never touched anything else since
- it does GF deco if you care about such things. Personally I'd rather not have my rebreather controller doing anything other than controlling my rebreather but it's there anyway.
- lots of battery options: simple AA, disposable lithiums, rechargeable. Can run on 1.5V or 3.6V as long as it is in the AA package. I use 14500 rechargeables and it lasts a hell of a long time
- Kevin is really supportive. At least in my experience.
Negatives
- it can be a bit flaky if you use disposable AA's in cold water. If you dive cold water then you really need to be using only 3.6V batteries.
- the depth sensors can be a bit of a weak point. Personally I've never really had any issue but I know others have. They are easy to swap.
- it's very expensive. But so are all the other options.
I've known a few people with AV1's and heard nothing but horror stories from them. I know someone who swapped to a JJ because he had so many issues with an Inspo with an AV1 fitted. I personally wouldn't buy anything that relies on support from Russia either.
Another option might be Laguna Research. They made very good controllers that come up for sale occasionally. I think the big problem was they were ahead of their time, the recreational rebreather market just wasn't there to sustain them. Their products were really highly rated though by people I knew who used them on Mk15's. I think Wayne is still making control systems under a different company name now. Someone else may know more.