Should I go for this?
If you've got the cat point and generics to spare, the answer is an almost unqualified
yes, strictly for elemental harmony. It is
incredibly useful.
This yes goes from almost to completely if you've got access to an easy source of acid or fire self-damage, especially fire. Staves are good for this with non-magic pumping classes, flaming or acidic iron daggers for most everyone else. You can use the attack talent to target yourself with a melee bump.
Elemental harmony's fire effect
stacks with most other sources of global speed. This can get faintly ridiculous, even after its nerf and the recent change to global speed stacking. The acid is pretty good too, especially if you've got a hefty amount of healmod tucked away somewhere. None of the other effects are exactly going to hurt, either.
--
Stone touch isn't very impressive, unfortunately. It's good for chaff, but a lot of stuff you'd
really like to use it on (bosses, some elites, most uniques) are flat out immune. It's also not very safe to actually use until you get it to tlvl three
The only top tier things in the stone alchemy tree are imbue and extract gems. Gem portal's alright -- it's a poor man's probability travel -- but a nice tele rune or conveyance staff's probably going to be more helpful.