Well, you all have your points i can agree with, but Haze and JD you shouldnt forget that there are frontends that manage more than just MAME. You shouldnt "cater to other peoples' frontends", but anything "cool" on other frontends, distract people from main MAME and let them move to where ever they *think* it is cool. So from time to time, something new and fancy and most important, unique for main MAME, will keep people using only main MAME. With unique i mean something, that only MAME benefits of and not a external frontend. Like Calamity merging GroovyMAME into mainline MAME, that unique i mean.
So i dont think that EoceneMiacid ideas are bad. Especially when it comes to message boxes and in particular the nag screen. I could imagine having nice shader effects, while blending the different messages for example. I mean people only want to get rid of them, as they are seeing them as "ugly" boxes.
Now, i play most of the time on a CRT and i am very fine with how it is now. Because everything has a meaning there and fits perfect into a CRT setup, like the border outlining the game display area. I instantly can see if a game is cropped and how it is meant to be displayed, also if the font is looking good, i know everything is setup right. Anything too fancy here, could distract from that valueble info or even destroy it, as there are not much pixels left on a CRT screen, but for transitions between the screens, there is still room for any "cool and modern appealing".