There are some great bass luthiers making great basses.I have played the Adler 11-string and Al Caldwell's 11-string,which is a great instrument.
I have had a chance to play the Adler 4,sub contra 4,5,6,and 8 string basses.All play easily and are comfortable and sound great.He puts the same excellent craftsmanship into every bass he makes.
The famous Adler neck is a plus. Where else could you get a neck that's less than 3/4" thick that doesn't move ,bend or warp?
What I like best about Adler is that he is innovative. (11-string, 12-string)When we couldn't find a guitar string manufacturer that could wind a ball end on a .004 wire,Mike designed and patented a clamping bridge system.When I approched Mike about building a 12-string bass guitar several years ago,he took on the challenge and got it right the first time.
His basses are tough,sturdy and look great.Do I think Adler basses are for everybody? No.The players I've seen using Adler basses seem to be discerning bassists who have specific needs in a bass,and don't want to have to compromise.