i am another proud 155 owner!
i have sprayed both acryls and enamels, aswell as automotiove paints, and it sprays all with out any problems.
dont let the fact that its a double action put u off coz its real easy to master
as for thin lines, im not sure, but id say less than about 5mm??? i havebt really pushed it, just saw what i could do with some left over paints. tho, if ur after finer lines, u may wanna go with the badger 100lg, coz its grav fed and can spray at lower pressures, meaning finer lines...
hope this helps!!