FWIW, it seems to me that on  my Ubuntu laptop the GL behaviour is different whether I access it "directly" or via GLEW, with the GLEW version being "better". That *might* also be a factor for your test?

<random_tangent>

As an aside, I find GLEW a bit odd, in that it is distributed as a library, but in fact if you look at the source it is basically just one header file and one source file... so you can just include the header file (in place of the usual GL header) and link the source file into your code and it Just Works. (I often do it this way on Windows, since the stock mingw lib that the GLEW configure script builds doesn't static link properly, a fact they seem to know but not be bothered by... I have also done it this way on Linux, on occasion, simply because it was in my Makefile like that...)

-- 

Ian