Em Maginn:
I think you need to wait a while before you finalize your theme design. The iGoogle "New Look" is not available for all browsers, so right now you'd have to design your theme to look right in both old and new versions. Also, the repositioned search bar now "floats" to the left, meaning it will obscure different parts of the header depending on the width of the display window. I haven't yet worked out a way to design a pleasing theme that will satisfy these criteria.

I'm hoping that Google will respond positively to the comments of theme users and developers for whom the new look has destroyed previously well-designed themes, and return to a smaller fixed search bar.

You might like to make some comments in the more relevant discussion here:
The iGoogle "New Look" from a theme developer's point of view
http://www.google.com/support/forum/p/Web+Search/thread?tid=61553ac38f323be2&hl=en

And also provide any relevant feedback here:
Share feedback on Google's new look
http://www.google.com/support/bin/request.py?hl=en&contact_type=surveyk&ctx=go