Browser detection in default template

I am currently converting all the jquery scripts in the default template (v1.5.5.1) to be compatible with jquery 1.9 and need some guidance on the use of $.browser in the product template. The code is as follows: It only sets this if the product has options.

Because I am converting the default theme to be based on the HTML5 Boilerplate, and it loads modernizr.js in the head, and all the other JS in the footer, I would rather test for the lack of a feature (using the html class="" that modernizr inserts) than use this removed jquery method of browser detection.

I think it is the only missing method left for me to remove before I go totally 1.9 compatible and remove the jquery-migrate.js shim that simulates these old functions.

So can anyone tell me what feature is missing in IE6 that causes us to need the .bgIframe() method?

I am guessing it might have something to do with the jquery-ui popup calendar type tool, but I have been at this theme conversion for a couple of days now and brain fade has set in <grin>.

Did you ever work this out?
Been working on something similar to what you seem to be doing.
Updating all the JS in 1.56 so it works off a CDN seeing load times of around the 3 sec mark (far better than the clients current install which is 15+sec).
I've replaced all the deprecated code except for the browser detection although I am half tempted to just remove the code completely as it would only effect 0.5% of the sites current traffic.