Any guesses on how many "To Do List" apps are going to be available within the first month? Note to to do devs: I've got the killer To Do List app framework - it's a spiral-bound noteback and a cheap Bic pen. Problem solved.
Seriously though, kudos to Yahoo for this. I'm honestly very excited about the potential for creative new apps that can be built on this platform.
It's probably true that Gmail has this on their roadmap. I would recommend those who aren't already building a product to create something on Yahoo and see which ones are "hits" and be ready to port to Gmail asap. Good luck, this is a great opportunity.
Actually if you have been using Zimbra you will notice that this is the same as the Zimlets feature. I know Zimbra is owned by Yahoo but this is an open source project and people have been using it for a while.
