I'm currently doing a refinance with PenFed. There have been numerous delays and I think they're mostly overworked right now. Most of my correspondence seems to happen after their normal business hours. Total processing time is running about 6 weeks for me, but the loan processor assigned also quit the company about halfway through, so that added to it. I do like how streamlined their process is and their rates were about the lowest when I was looking around.
That said, when we were selling our home about 2 months ago, a lot of agents I talked with recommended local lenders. They said there have been so many problems with appraisals (either delays in scheduling that pushed the closing date out or values coming in low) when dealing with online lenders, that sometimes sellers would choose between competitive offers based on which bank was being used. The idea being that local lenders had a more reliable set of appraisers they engage with.