It is one of the reasons I've been looking at XSLT/XML pages. The XSLT files are totally cachable, so when you're looking at similar pages of content (i.e., forum posts) you can use the template over and over again.
Javascript's cacheable too, and if you use one of the free public CDNs for jQuery, chances are it's already cached on the client's device anyway. Microsoft's CDN even includes the templating/binding extension, which sounds ideal for what you're doing.
Forj Forum