In the past I've been responsible for Exchange, SQL, and Dynamics CRM. I've had the same concern about cumulative updates - even service packs. You know you need to, so you do the risk/reward algorithm.

The part of that that bites me though is when you decide the risk is not worth the reward, but then two CUs later, you need to roll-up because the most recent CU meets the risk/reward threshold; so you need to take on the risk you weren't willing to before, for the reward you want from the new one.