I agree that it is a great bittering hop.
To explore the flavor and aroma aspects, I just recently made an extra pale ale with Summit hops.
I was hoping for a "tangerine"-ish extra pale ale and was sort of disappointed with the result.
Maybe it was a suboptimal batch of Summit hops, but maybe not...
It was a good base recipe I've used before with great success with the proper attention paid to grain bill/ water profile/ mash temps/ sanitation/ temp-controlled fermentation/ yeast/ etc.
Jeff and Sean's comments seem to mesh with my experience.
I single hopped using the all late hopping method--25 minutes or less for all additions, including aroma steeping for 20-30 minutes (when T<170F during whirlpool/chilling). Very smooth and vaguely "fruity" flavored but not much aroma which may have been lost due to CO2 scrubbing during fermentation and/or adsorption of hop oils to the yeast.
Since the aroma was disappointing, I dryhopped in the keg (1 oz pellets/5 gallons) and got better aroma, but, as Jeff describes, there's a not-so-great onion/garlic component that is quite noticeable and unexpected.
Initially, I thought I had somehow infected the keg during dry-hopping. But, it is all coming from the Summit hop.
Like Sean says, there probably are better (cleaner smelling and tasting) choices for late additions and dry-hopping.