Avids are fine as long as you steer clear of Juicy 3s (perhaps the other Juicys but have no experience of them so can't comment).
Elixir range is fine generally if treated right.
Biggest problem I feel is too many people jump in and start bleeding them. That's where problems start to begin. Stop bleeding and try making adjustments.
Change pads for starters. "Squishy brakes, oh bleed them" when it's the pads are worn right down. New pads, firm braking again. Fiddle with the bite adjust if you have it. Though I find the Elixir and higher X series stuff self adjusts for wear so there's less fiddling required (Juicys never adjusted).
Good trick if the levers are pulling to the bars or squidgy - wheel out, lever the pistons right back (flat bladed screwdriver or a pad spreader tool), one to two little squeezes on the brake lever, and put the wheel back in. Trust me, it will be loads better
On the bleeding, if you really feel you must, first try overnight tying the levers to the bars with rope or cable ties (with wheel in or with pad stoppers), and leave it like that. Next day chances are it's loads better. Though probably indicates it really does need a bleed if you keep having to do that. I've only ever had to do that with Juicys though.