Anybody deal with member "Ronni"

Anyone know how to leave feedback?

Yep.
1) Click on the username
2) Click the tab marked "FEEDBACK SCORE" (this will also let you read the feedback rating and comments of others)
3) In the ITrader Profile select "Submit Feedback For XXXXX"
4) Follow the instructions. Note: You will need to know your transaction number (the post number of the for sale ad) so before you do this, go to the ad and highlight/ click COPY the post info in your browser bar and COPY into the "Deal URL" box.

I STRONGLY recommend you do not leave feedback if you are the buyer UNTIL THE SELLER HAS LEFT FEEDBACK FOR YOU! The seller gets the money first; the onus is on him to report a satisfactory sale. After that, it's YOUR responsibility to do your part and follow up with feedback on the purchase as the buyer. Sometimes it takes several PM's to get a guy to leave feedback once he's received his money...that's OK! Make it clear that you will return the favor once feedback is left for you...and then make good on your word. Money changes hands before parts; feedback needs to follow the same path.
Plumkrazee, if you are happy with the transaction make sure you leave feedback for Ronni so he can avoid this in the future!!!! And vice-versa for Ronni....