Progress in which games are emulated should be made at all times, but you should always still refine problems with old games, and put things on a halt if it's a show-stopping bug. Say a given game or games freezes a system or if the sound of a guy having a hernia would be favorable to the sound a given game runs with. 500 games running decently if not perfect is better than 700 games running like crap. Emulators should focus on whatever they want to focus on. MAME focuses on accuracy, and preservation itself, and portability.
SPeed is an afterthought.
So far, it's worked out pretty damn well for us when the emu authors just did whatever came to mind. Since they seem like pretty self-motivated people, I think we should just leave 'em alone and let 'em do it the way they want. Try one of these sites, each of which features access to several emulators. It's interesting stuff, dammit. The only reason I'm posting this mail is because I hope these guys make enough money off these retarded sneakers to buy themselves a clue.