I own 2 A-Bolts. One is a 7mm Rem Mag (the most accurate rifle I own, and I own ALOT), and a 25 WSSM.
My 7mm will shoot 1.25" groups at 300 yards, at 100 yards they are usually in the .4" range.
The rifle isn't quirky at all, both of my a-bolts have shot everything I've loaded for them equally as well. When I first started playing with my 7mm, it shot the 139gr SSTs so well I didn't want to change. Then I tried the 140 Accu Bond, then the 160 Accusbond, then the 160gr TSX, the the 175gr Partition, all the way back to a 120gr TSX. It shot all of them equally as well, with the 160gr Accu Bond being the most accurate load I've ever fired from that rifle.
The 25WSSM I haven't gotten to play with much yet. It shot the factory 115gr Combined Technology BTs around 3/4", and now I have all the loading gear, and alot of bullets to try. So this summer I'll update on that.