Mick - I spent a few days in an RAE simulator a good while back looking at handling qualities of stabilised and unstabilised helos - all to do with anti-tank ops and low level manouevring. We also looked at reduced visual cues and what was the best mix of HQ and cues - the worst case was an R22 in cloud where 90% of the time a crash was inevitable especially when any other pilot tasks were introduced.
As the level of stabilisation was increased so the survivability of the IMC encounter improved.
The answer to your question is that you fly with it on all the time or there is no point in having it fitted.