I despise the ebay/paypal fees but each route of selling/buying used gear has its advantages and disadvantages.
With eBay you reach a larger market. It's also a good place to sell if you don't really know the value of what it is you're selling. I recently sold a 34mm Alpa multi use adapter on eBay that I had no luck selling on GetDPI, and actually got more on ebay after fees than I had it advertised on GetDPI for. I've also gotten lucky and found some crazy deals on eBay, and have actually made money buying on eBay and then selling the same things elsewhere. I've gotten good money for some used Apple products I've sold through eBay that I thought had little to no value.
The forums I find are better for the buyers and the sellers if you can trust the buyer/seller. I've bought stuff and sold on GetDPI (645z, A7RII, various other stuff) and LuLa (Alpa STC, various random other stuff) and haven't had any issue. As a seller, you're able to often get more for your item than you could on eBay since you don't have to deal with fees, and buyers are able to get things cheaper than they can through eBay since sellers don't have to deal with fees.
I've also sold plenty through Craiglist (guitars and camera gear), which has its pros and cons too. You have to deal with way more scammer/low ball types, but serious people usually come through and buy that know their gear and make reasonable offers...and I end up making about what I would on eBay after fees with cash in hand. Last thing I sold on Craigslist was the A7RII I bought on GetDPI and was able to get more for it than what I advertised on GetDPI because I didn't have to deal with paypal or shipping. Have had good luck selling guitars on Craigsist too, which saves the stress of having to ship the guitar.