For me, the biggest hurdle to selling my personal items online is flaky and/or malicious buyers.
On Craigslist, buyers tend to be extremely flaky. Every time I've sold something there, I've wasted substantial time with
people who arrange meeting times and don't show up. This happens many times per item. It's also overrun with scammers, although those are easy to spot if you know the signs. (Bad grammar, being unrealistically enthusiastic to the point of offering more than the asking price, mentions of out-of-state or overseas transactions, etc..)
On eBay, you have the ever-present risk of fraud. A typical scam goes something like this: Someone buys your item, you ship it, the buyer files a dispute, and eBay/PayPal take back the money. The scammer was planning to file a dispute all along, even if you did everything right. There's very little you can do to combat this, in part because eBay tends to favor buyers over sellers.
If Sold takes on all the hassle and risk of consumer-to-consumer selling, then I'll definitely consider using it.