I have successfully imported my contacts, but I can't add my yahoo address as an account to get mail from only one to send mail from?

When Yahoo Mail will support POP3, you'll be able to import your mail in Gmail. Right now, the paid Yahoo Mail and some international versions of Yahoo Mail (e.g.: YMail UK) support POP3.

People should have the reflex to opt for open apps, and leave the day they close their doors (or complain enough to make the apps change its plan).

Most people have no idea what burden it will be to be locked up in close gardens (even if you want to change, you've to give up lots of data and make the effort it took to organize it a complete waste of time).