I have collected the following statistics from our Canvas game, using a dummy-gl thread:

Percen   Renderer
25.7%   Adreno
25.7%   Q3Dimension MSM7500 01.02.08 0 4.0.0
15.5%   PowerVR SGX 530
12.3%   unknown renderer
11.9%   AMD Z430
6.24%   FIMG
2.19%   Android PixelFlinger 1.0
0.11%   PowerVR SGX 540
0.08%   Android PixelFlinger 1.2
0.01%   Android PixelFlinger 1.1

Note that 'Android PixelFlinger ' renderers are software renderers. The tattoo uses Android PixelFlinger 1.0 and that one is definitely way slower than canvas, and makes our game (in its yet unpublished gl-version) run crappy. I don't know if the 1.1 or 1.2 version of the pixelflinger runs a lot better. I believe the rest of the renderes are hardware renderers, and that they are the names of the chip.

So making a strict gl-game you may loose 2% of your customers due to bad performance. That ofcause does not include what you may gain using opengl due to better performance and/or nicer graphics.