I may actually be experiencing this afterall. When I see a hill I take it out of overdrive, it helps, holds the gear longer. However... I've also felt a weird hesitation at times, and I think this might be it. I'd describe it as an, odd sounding, lag in response. It's trying to accelerate while the rpms are at/around 1400, but it won't gear down.
I think it's time to get a tune - I'm gonna have to go for it.