For PIX alternatives, you might want to give apitrace a try. Valve's Linux team was raving about it at this year's SIGGRAPH OpenGL BoF.

http://apitrace.github.com

Still receiving frequent updates and new features. It's been exciting to see it come together.

My biggest caveat has been the OpenGL ES support on Android. It only builds properly on Linux, and it doesn't support performance profiling the last time I checked. You're better off using vendor specific tools like Nvidia's PerfHud ES for Tegra devices and PVRTrace for PowerVR devices for that sort of work.

There's also no support for OpenGL ES on iOS devices. Fortunately, Apple's OpenGL ES profiling tools for Xcode are (surprisingly) quite solid, and much less of a pain in the butt to set up than any Android OpenGL ES solution. As long as you're content with there being only one game in that town.

EDIT: And for taming GL Extension Hell, GLEW is still the best; http://glew.sourceforge.net . If you see a tutorial that suggests anything else, it's wrong. :)