The GovDeals gap is real but honestly the core idea is solid. Bought a monitor arm through state surplus last year and the discoverability problem is brutal. Even half the sites aggregated saves hours.
I used to work for the company that owned and operated GovDeals. That was a really interesting experience. I remember one of their many companies host the listing for and processed the sale of an oil refinery (or something similar) just like something random on ebay, except this sale was many 10's of millions of dollars.