My two pence...
Regs go belly up, I've experienced it and it can be subtle enough to mess with your head and can take a long time to work out the cause. Two out of three of my reged rifles needed a reg rebuild.
I see fellow hft'rs reged rifles go funny, quite common, we had one yesterday at cambridge with the comment being something along the lines of 'Bl**dy reg!'
They dont make your rifle any more accurate.
They generally make your rifle have a larger shot to shot variation, comparing the sweet spot of an unreged to a reged rifle.
Despite the hype a reged rifle will often still have a sweet spot, an area in the fill where they shoot better.