Try not use VBOs then
The question is, why they push the use of a new feature if it's not implemented well?
Conclusion, even with traditional glBegin/End you can get an outstanding performance as long as you algorithmically optimize vs. instruction/pixel/hardware optimization.
Personally, I only believe in hardware rasterizer as an alternative fast way to software rasterization. Other than this, try use a pure shader path and see if it's slower or faster