I generally sell locally on Craigslist, but recently have had a few items not sell after listing for fair prices (lower than MPB/KEH/B&H/Adorama used, but above what MBP/KEH offer to buy).
Full disclosure, my first experience with MPB was a bad one. The initial part was fine – online quote, shipping label provided, items received. Despite their promise of 2-3 business days, I heard nothing for 6 business days so I emailed them. They replied a couple of hours later with the email requesting my banking information, which I provided. The next day I received an email saying payment had been made and would be deposited within two business days. The funds didn't arrive, so I emailed them again and they replied they would look into it. Again I did not hear back, so a day later I emailed them and they said they were having trouble with their bank making payments and were looking into it. They did eventually get it sorted, but in all it was about 3 weeks between them receiving the gear and me actually getting paid.
I have subsequently used MPB for other gear on a couple of occasions, and that went wha seems like the norm for them - about 5 business days from them receiving it to the money being in my account, and I did not have to email them several times to move things along.
For those selling gear, it's worth checking KEH as well. The offers vary, for some items one or the other will offer ~10% more. If it matters, KEH's evaluation and payment timelines are a bit longer than MPB's, and MBP does a direct bank (ACH) transfer, while KEH uses PayPal.