FANTASTIC!!! I just planted half my garden last week. Going to do the other half next week. I will use this and recommend to a few others on my garden project...its my first time ;)

I think your pricing segments make sense.

Recommended quick fixes:

1 - first email I received has the "Plant xyz" list. Great, but maybe also include a link in the email that takes me back to my http://sproutrobot.com/<username>; page so I get this same info and also the related instruction links

2 - from the email header it looks like your using gmail directly for SMTP. If so, you'll hit a limit soon on daily sends at 500(?). I've been using sendgrid and critsend for these type of email...both are easy to setup and both are reasonably priced for a startup.