The hills approaching the twisty part of Lombard Street in San Francisco are remarkably steep. I much prefer to simply drive up such a steep hill though I had to stop behind several other Smarts. Getting moving seemed awkward - it may have been the hill assist doing its job - but I got moving without a long delay. It certainly felt strange, though!
So - going up very steep hills: no problem at all.
Starting in the middle of a steep uphill from a stop? Awkward for one try, but no problem.