My feeling is, if you don't like the upgraded/trained su-26, you won't like arty.
Eh... depends. The turret is really, really nice. But it also has crap range, and the damage isn't particularly amazing - not that it is bad, it just isn't great. Range means a lot for arties, especially now that tracers are back in.
For a good low tier arty to try out, I'd suggest the T57. The next one, M37 should also give you a pretty good feel for arty.
Despite going up the Russian line right now, I'd stay away from it if you are trying to figure out if you like the arty playstyle. The SU-18 is horrible, the SU-26 doesn't really play like any other arty, and as I'm finding now, the SU-5 is also pretty miserable.