I've had my SQ-A kit for about 5 years with fairly extensive use, and have never had any problems with the electronic shutter being faulty. In fact, I haven't even had to replace the battery yet! The only real issue that I've had is replacing the light trap / seals on my 120 and 220 backs, which I consider routine maintenance with most older camera gear.

I've been very happy with the SQ-A.