I think W:S is good enough. Remember HTC Hero and Legend, which had some 600Mhz processor and still were good? Gingerbread takes much less resources than Eclair/Froyo which means that W:S should be fast enough given the price tag.
Yes I do agree that Legend was one of the best offering with similar specs that of HTC Wildfire S but it was back then, more one year back.
IMO a 1GHz offering should be a minimum one should look for in order to be a bit future-proof(I know there is nothing much like future-proof in world of technology but even then...)
Imagine yourself with a 600MHz smartphone after a year or so, it will feel pretty slow and outdated when you will have quad-cores entering in Q4 of 2012.
Also I don't reckon Wildfire S will get any further update other than 2.4(Icecream Sandwich) at max.
These are just my views, sorry to hijack the thread