They have had the checker for awhile as you need to verify your phone prior to listing. I have sold a few phones and bought several from Swappa. Just keep your eyes open and you can find some deals.
Much better deal than eBay as they charge 10% eBay fee.
Swappa at $10 plus the $5 flat fee if you want your listing as a featured listing is a bargain IMO. It gets a lot of action as well, but you deal with lowballers everywhere.
If you are selling newer phones (S4, One, etc.) your eBay fees get into the $50 range as compared to $10-$15 on Swappa.