I have a feeling what you'll end up actually creating might be significantly different compared to his original idea. Paul Arden makes a good point about ideas floating by on a river of ether, free for anyone to pluck out. So, while he presented you with the idea, it'll probably take shape as something else with your execution. Plus, execution is 99% of the whole problem anyways.
I don't know if I'd put the Kindle Fire on this list, it's really in a class of its own. Sure you can load Android apps on it, but it's mostly a way to consume media purchased through Amazon. As far as I know, you can't easily access the Google Play store, and as a dev, I know I'd have to reconfigure my app to make it available on the Fire. (I use in app purchasing)
I'm fine with wearing suits on sales calls in the right contexts, but it's more about wearing what is appropriate. At YC (or really any tech event on the west coast), a suit isn't appropriate -- at most, a button-down shirt w/o tie and MAYBE a jacket in the evenings.
It's kind of obvious when the guy on the other side of the table is wearing shorts and sandals that perhaps a suit and tie is inappropriate...
I can't speak for the US west coast, but it seems to me a good start is to actually know how to wear a suit. It absolutely has to fit correctly and be the right size. Unbutton your jacket when you sit. Tie your tie correctly and tighten and straighten it, top button of your shirt buttoned - OR loose it completely, opening the top button - there is no middle ground.
For me personally, I've always worn suits to interviews, but they haven't been for hacker positions. For me it was to show that I took the application process seriously and I really wanted the position.
I'm in the same city as you and I wear a suit... but only to interviews. Wait, I guess I wore it to my brother's wedding, too, but other than that it stays in the closet.
