What do you use to make codeigniter app's GUI more usable and faster?

[eluser]CARP[/eluser]
Hi guys
I guess the subject/question resumes all.
I'm starting development of a (let's say) big app with codeigniter, and the main request for it is to be:

1- fast. Not only fast loading but to have less requests and reduce page reloads
2- usable
3- responsive

I solved some items by going with a simple lightweight twitter bootstrap, but would like to learn which other tools do you use to make these things possible and to accelerate development of these

For example: a jQuery plugin for MDI windows, and such

Thanks!