I think most people would advise avoiding gradients wherever possible - what might seem "interesting" on paper will most likely be a pain in the a*se in actual operation.......
Visiting a local GSS member's open day this year I took my Piko BR24 and the rake of four 6-wheel rekowagen coaches (which are pretty heavy, admittedly) - none of the gradients on his line were anything excessive, in fact they were gentle enough to be barely noticeable to the eye - but with the full rake of four she just couldn't make it, I had to take a coach off to get her round the circuit.
Jon.