I wonder what the correct tradeoff is for you between making it easy for new users to see products, vs. getting signups. You certainly wouldn't want to require users to install the iPad app before seeing products, since that's a huge amount of friction, but even signing up for an account is a fair bit.
I'm curious if you analyzed your customer profile based on entry point into Fab at all? Do you see the same type buying profile (% of users with purchases/frequency of purchases) on tablet-first vs. web-first customers or are these high tablet numbers mostly a result of pre-existing web customers downloading the tablet app.
In other words, do cohorts of users signing up from a tablet actually outperform users signing up from the web, or are you just migrating users who are already engaged on the web to purchase on tablet?
Excuse typos I'm on a plane on my iPad ;-)
Very interesting stats in any case.