The OP and I must live down the street from each other. I have never done 30A Songwriters Fest for the reasons he mentions, it is expensive and crowded, so I stay away. But I have always wanted to go and will at some point.
My daughter went to her first Hangout Fest last year. I have taught her well, and she was all in to see the Lumineers first and foremost. She wants to go because of The Head and the Heart this year, but scalpers bought the damn thing out already and doubled the cost to attend. I have absolutely zero interest in being on a beach in the sun all day surrounded by 20 year olds, so I know I have hit the "get off my lawn age."
I am going with a group of friends to Mile 0 this year, they all went last year and loved it. I'm pretty pumped, since the set up seems great for me. We are staying in a group of cottages a block from Duval that was purchased as part of our passes for the concert, so there is a shuttle route and other perks (like a boat trip with performers) and the venues range from local bars to beach front concerts. Key West in January means highs in the low 80s and lows at night in the 60s or so. Plus the line up kicks ass.
A group of friends went to Steamboat for the concert the red dirt festival there, and the Winter Wondergrass seems like a cool deal too. I would go to either one of those with the right group. Bonnarroo has a fantastic lineup this year, but I'm too old for that scene. Bottlerock looks awesome, but that is the other side of the country for me, so it is unlikely any time soon.
Back in the day, the best I went to was the Sunshine Daydream Festival in Live Oak, Florida. It is a camp ground in the middle of nowhere, and there must not have been any cops for miles because it was like what I think Woodstock must have been like. Absolutely zero rules and drum circles throughout the night. Old and In the Way was the headliner, and it was mainly hippies dancing to awesome bluegrass.
Everyone knows Jazzfest in NOLA, but the one that is WAY underated is French Quarter Fest. It is all local bands, so it is a lot of Zydeco and brass bands, but the variety is awesome and it is in April so the weather is fantastic for just wandering the FQ and seeing a few songs at each stop. I haven't gone specifically for it, but have been there for other things while it was going on and loved it every time.