"the brain perhaps needs to be set before setting off for the kind of conditions expected & then probably best left as it's a pain to adjust, whereas the Triad shock can be adjusted on the fly depending on whether you are climbing, descending etc?"
Thats pretty much what I end up doing
"reliability issues with the Brain shock?"
I've had one shock leak (oil) and they managed to replace pretty much everything including all of the brain assembly (on warranty) for some reason?
"Presumably Mojo can service it….?"
Specialized warranty is 5 years kept valid by getting a full service done by them every year or so (£85, so about the same as elsewhere) so no need to send it to somebody else
I think its usefullness depends on what you want the bike for. For most riding I think I'd prefer it to a system where you have to choose. Its just when you start to take the bike to its upper end of its 'riding spectrum' as it were when you'd like to be able to get the most out of the suspebsion that It starts to become a pain, especially when you hot a road/smooth firetrack to go back up again. That said niether decending with the brain on, or climbing with it off, really makes much difference