My take on this now:
From experience here is what is happening on 2.0. You can reply to any email account that you have configured with the correct "from" and "reply to" address, but you can't change those to another address for your reply email. For new emails, you can select any account you have configured, plus your
address. If you select the latter, your settings on the BIS control your "from" and "reply to" address.
For Yahoo or an IMAP account, copies of emails from the BB are stored in the sent folder. Deleted emails are moved to the trash folder. Items sent from your email account and deleted from there do not appear or get deleted on the BB. Read and unread marks are reconciled from the BB to the email account but not the other way around. Thus, itís a one way sync unlike BES which is a two way sync. No other subfolder moves are supported. Thus if you use typically file messages on the BB and then choose to hide filed messages, you are out of luck right now. All the BIS messages will remain on the BB message list. Thus, get hosted BES for the best experience.