Looks really nice! Long time Sparrow fan and it'd be sweet to have a familiar experience on my Windows box too. Seems like they're developing a bunch of stuff on top of what Sparrow has too which opens up new possibilities of an email-orientated app store. Worth supporting on Kickstarter to help make it happen, plus get a license back which you'll end up buying anyway if this interests you.
I've outsourced a ton, spending >$5k over the past 8-years or so. I've written a little about how best to outsource through these platforms: http://www.keithmander.com/?p=243