Hi there! From what I've seen so far (3 days and booklink completed), Akelos looks like a nice tool to build great applications in a traditional MVC style, where M is back on the server (perfectly normal for a PHP project...). With the advent of Ajax, more and more logic is transfered to the browser so that the user doesn't have to wait for each step (e.g. validations).
What I would see as a big step forward is more advanced MVC platform with a MVC triad on the browser and a MVC triad on the server, to obtain a highly reactive application. See for example: www.sistedes.es/sistedes/pdf/2007/SCHA-07-Morales-MVC.pdf
I've been looking to different MVC platforms based on JavaScript for this 1° http://javascriptmvc.com This OS project is still evolving with 2 developpers. 2° http://www.sproutcore.com/ This is a more active OS project