Hi,
I am just starting to use Boost.Regex, porting from the Linux system regex library to Boost.Regex, and after doing initial testing on my first change I see a major performance impact, where Boost.Regex is about 30 times slower than the system regex library.
 
The Boost.Regex documentation seems to imply that its performance has a positive comparsion with existing libraries so I expect that I am doing something wrong but can't see it.