there is a bunch of widget classes that abstract out the underlying openGL in pymt. Check out the ui subdirectory in the pymt module folder. you can also check the API docs. For images and things like that pyglet itself has a bunch of helper functions. check out the pyglet.image module for loading textures from different file formats etc. (we even have an asynchromous image loader in pymt for loading images over slower network connections) you can get access to the openGL texture ID, but you can also just handle them as a picture, they have a draw/blit method. For other drawing purposes you can check the pymt/graphx.py file/module (or look in API docs), it has a bunch of helper functions for drawing shapes and things like that. The newest svn even has some beginning support for css styling of widgets (thanks to tito), which makes things easily customizable.
Using pure OpenGL fo all the drawing does make things a little more compicated(asumes some openGL knowledge), but as we get the framework worked up more hopefully we can have helper functions for doing all the routine things. OpenGL does give the performance boost you are talking about..and also lets you do really funky/custom things apart from 2d/3d if you want to/know how to. One major advantage I think, is that you can apply shaders to anyting you draw in openGL for some really visual cool effects (see mandelvbrot example...really its just drawing a square..all the colors/shapes are done by a shader)