I'm no expert on boost, but it's really going to depend on (a) which portions of boost you want and (b) how you'll be running vxworks (kernel vs. RTP) and what target.
Immediately, I'm looking to get boost::serialization working. We use vxworks on ppc boards as well as their 'vxsim' environment -- which is code compiled to run natively in the host environment. The sim environment may be running under sparc or x86 hardware, so we were toying with the idea of resolving endianness issues with boost::serialization. That said, it isn't the only one we're interested in using, it's just the one I'm focusing on at the moment.
6.5 has issues in many places, some targets more than others. Maybe consider being more specific?
We may be upgrading our license to 6.7 soon. Any problems in particular that may get in the way of using boost? I'm more or less looking for some sort of outline of what others have done to use boost in vxworks. Everything I've found while googling indicates others have asked and figured it out, but never posted back to the original forums indicating what they did to get it working, or otherwise got it working and had problems further down the road. Thanks for your swift response, I appreciate it. -Brian