This is what I found doing some timings:

For the short-circuit path, the regexp can make quote 10x as fast in
exceptional cases, even comparing to the faster version in trunk. The
average win for short-circuit seems to be twice as fast as the map in my
timings. This sounds good.

For the normal path, the overhead can make quote 50% slower. This IMHO
makes it unfit for quote replacement. Perhaps good for a cookbook recipe? 

Regarding the OP's use case, I believe either adding a string cache to
quote or flagging stored strings as "safe" or "must quote" would result
in a much greater impact on performance.

Attaching patch against trunk. Web framework developers should be
interested in testing this and could provide the use cases/data needed
for settling this issue.