Since we do not have a feedback/rating system for sellers and buyers on the marketplace yet you can use this thread to name the people you did good business with.
If you prepend an @ to a username, a link to the persons profile page will be generated.
The thread is searchable so it should be easy to find users with a good reputation over time.

Edit:
We now have a simple user rating system!
On every users profile page you can vote up or down your experience with a user.
You just vote the user one time in general, no single transactions. It does not matter if you are the seller or buyer.
The accumulated votes will be displayed on offers and in the user profile.
You can always revoke your vote by clicking again on the thumb button.

To get started feel free to rate users you had transactions with in the past.

Beep, Bopp, Bleep: info@modulargrid.net