I essentially get offers via GD marketplace everyday now, so I'm really torn about it changing my set-up.
Use the marketplaces as a tool but do not use them to sell because the 20% commission is better off in your pocket.
The way I look at it is my domains get constant exposure at godaddy because they are listed at twenty bucks. Once people bid 5 or 6 times and see they get no response they will simply type the URL in the address bar and contact me directly.
It is a beuty, your domains are listed with massive exposure and your sales go up from your home page. The occasional time when a really good offer comes in you can always take it and give godaddy the sale.
The important thing is your email filter, make a folder and direct all godaddy auction inquiries there so you can peruse them at your convenience.
Now here is the part I have not mentioned so far
You can log into your godaddy auction panel and click on the price and it will sort your domains from the most offers to the lowest. It will show how many bids per domain etc and that will allow you to determine the activity and all still for free without ever costing a penny.
I have an article I'm working on with something new and interesting I will be posting this weekend and it contains some eye opening material. I did a head to head experiment with 250 domains vs 250 domains and I found a strategy that made a dramatic difference in my sales.
Stay tuned for that one soon.... I will post it on my new blog and link it back to here.