GL ES support is not as easy as flipping a switch and it's not something i'm going to look into until it's clear it's the best way to get where i want MAME to be. There is no 3D rendering going on in MAME--it's all emulated--and from the few conversations on drawing performance i was privy to, the memory bandwidth of the device is often the limiting factor for graphics-intensive apps. I hope someone who knows the details better can pitch in with better knowledge, but my understanding is that without independent RAM of its own to use, bringing in the GPU for drawing can actually reduce performance because of extra transfers to/from RAM. Whether that's actually the case or not, the limitations of the N900 hardware compared to a PC are such that i'm not at all sure that GL ES is going to be worth the effort. I haven't done any detailed profiling yet since the update.

Regarding the question of how much the PR1.1 system updates influence SDLMAME performance, here's what i found (using just a single older ROM):

No hardware scaling: 34% -> 52%
YUV overlay: 86% -> 88%

Which is kinda what i expected as mentioned earlier.

One interesting thing is that the kernel is now more occupied during execution than the mame binary is, in either case. I'm not sure what that means, but it suggests that the actual emulation is still the minor part of the cycle usage.

It's not a great secret: i clearly mentioned it's in -devel, meaning Extras-devel. It's a place for stuff not considered ready for users.