David Reveman, has posted his thoughts on the Xgl/Aiglx debate here:
One of the points that I particularly like is:
An important goal with X on OpenGL is to make it easier for X to keep up with the advances in graphics hardware. Eliminating the custom 2D acceleration code will reduce the development burden and make this easier. This can probably be achieved through AIGLX as well, I know that the people working on AIGLX have discussed putting some of the acceleration code I have in Xgl inside Xorg with AIGLX and that would be a step in that direction. However, I strongly believe that going all the way to an X server completely on top of the OpenGL API is the best solution in the long run.
In particular I like his comments on the criticisms of Xgl, they all boil down to "It is a lot of work":
I think the arguments made by nvidia to why X on OpenGL would be worse than the current driver architecture can be debated on until forever. I think it all boils down to if we want put some more effort to it and take the big scary step to something new or if we want to stick to the old well known. Not too surprising, we have people who are in favor of both and we'll likely have development being done on both, which I don't think is that bad after all.
So far I haven't heard a single argument for why X on OpenGL is a a bad idea other than that it's a big step and a lot of work will have to be done. If that would stop me from working on Xgl, I wouldn't have started working on it in the first place.
Finally, David sets the record straight on the Xgl development, to refute the claims made on the Fedora page:
"We've been working on the AIGLX code for a some time with the community, which is in direct contrast with the way that XGL was developed. XGL spent the last few months of its development behind closed doors and was dropped on the community as a finished solution. Unfortunately, it wasn't peer reviewed during its development process, and its architecture doesn't sit well with a lot of people."
I've been developing Xgl in the open since November 2004. Only the last few months have been behind closed doors. I can agree that this wasn't the best thing but no architectural changes have been made during this period, just a lot of hard work implementing missing functionality, tracking down and fixing bugs in xgl and various other places in the x server tree. We didn't drop a finished solution, we dropped a much improved version, that's all.
Anyways, more details are on David's post