Shouldn't this first check if Chrome Frame is actually used (by using the User-Agent header) before it injects the code? And why not just place the four lines straight into your layout?
I feel like a complete jerk for saying this (partly because Sunlight Labs is a non-profit), but it suffers from what I like to call the snippet marketing syndrome: 4 - 5 lines of code being fancied up into a 10 - 30 line "plugin" with heavy references to the consulting studio that 'coded' it.
The idea behind Rack middleware is that it's incredibly easy to implement for the developer and re-usable across the spectrum of Ruby web apps.
Yes, implementing Google Chrome Frame in a given app is trivial. But removing this from the concern of a given app and into a re-usable middleware is where I think it's useful.
I think the biggest disadvantage of putting something like this in middleware, is that it's completely incompatible with stuff like memcache. The injection of this meta-tag is done after a memcache SET would have been done in the web app, and so if you have a reverse proxy in front of your webserver, for any cached page that's served, it won't include the injection. Also, the user-agent check that's being done in this plugin yields incorrect results in the presence of caching for similar reasons.
Didn't use the plugin but used the code snippets on a site just to test it out and.. I think Google need to slicken it up a bit first. The installation overlay blocks out most of the site on IE6 and doesn't seem to be closable. I'm guessing this is really meant for sites that demand it be installed rather than an optional thing - but if that's true, why not just redirect?
