The goal is to complement the contacts applications, even replace it. It uses the "same database" and accounts. Currently, the only integration is that you can click on the "contact avatar" in order to use the "standard contacts" application to edit the contact info.

So a powerful management of address book is a really urgent thing in n900!!!!

Check the FAQ. Later I will try to make it into a setting.

That is a limitation of the phone. The only thing I can do is to have the application convert the mp3 to wav automatically (exactly what the "standard" application does).

It is in the plans.

Any application that works with the phone will work (there is only ONE contacts database - the only information is stored separately by mycontacts is the groups members.