You are worried about nothing. The person you heard about had an unusual case.

Both the Ford Escape Hybrid and the MMH have a CVT. There's no gear shifting! There's only one gear ( with an infinate number of ratios ).

It is normal for the engine to rev over 5000 RPM on hills at highway speeds.
I can take 12% grades at 25 miles per hour with battery pack alone ( for about 30 seconds )

The battery pack can provide up to 2 miles of power over flat roads, and at speeds under 40 miles per hour. At higher speeds and on hills, the battery boost time is probably about 30 seconds. But don't worry. I've always been able to pass semis, even on 7% grades and 10,000 feet in the Colorado rockies... however, since this eats a ton of gas, I tend to stay behind the semis on up grades on purpose.

If you intentionally follow the speeds of semis, you will get about 24 MPG up the Grapevine, and about 64 MPG on the downslope, which will = a great average.
-john