Eligibilty to raise an unpaid item dispute occurs on the 8th day after the listing closed and will be visible in your 'My eBay'.
Once raised some pay up, some ignore, some argue.
Whatever you do do not get into a slanging match. Send 2 or 3 gentle reminders over 7 days. If no payment arrives raise a dispute and then get on with other more interesting things.
eBay will mail you if they respond. If they do not respond within 7 days you can close it regardless and claim back the final value fee and relist.
See earlier post in this thread regarding non-response and feedback options from biscuit.
Oh and I usually block them from bidding in future, this option also becomes available on dispute closure (but can be accessed any time).
Regarding feedback, buyer first, seller second.
Why ?, sellers who give feedback even after payment are asking for trouble. The 'deadbeat' buyer is then immune from receiving a red from you and can do whatever he wants. He has increased his profile postively and further enhances his cloak of respectibility ready to sucker another generous seller.