I don't have a HH rebreather, but I dive a HH on my Mk 15.5. I have over 110 hours this set and have had no major issues. I've ordered an extra HH for my unit so that I can check out the delrin handsets and this one will have a HUD.
I've been diving HH electronics since the days of the clear ones, and I'm really happy with my current set. My feeling is that Kevin has worked out 99.9% of the prevous bugs of old handset revisions and now offers an awesome product. You can even get them on the phone now (without even having to call 50 times in a row to annoy the $hit out of them).
Keep up the good work Dude!
Aloha,
Charlie