Constantly.
Seriously, for 1 point, it's incredible. You'd be crazy not to get it.
Or let me put it this way... the DPS gain is an extra swing every 10 seconds. So, take the average damage of your current weapon(s), divide by 10, and that is your DPS gain. For me at lvl 47, that equates to about 24-26 DPS. Not to mention the 2 subsequent boosts in nature damage. That means 1 Earth Shock for 20% more damage, and 1 lightning shield ball at 20% more damage.
Note also that it doesn't interrupt (that I'm aware of) your current swing timer. So if you run up to a mob and SS, you basically swing instantly twice, Earth Shock and Lighting Ball, and the mob should be at about half health. If you're dual wielding, you will probably have proccd WindFury and/or a crit, so you theres a good chance of gaining Flurry and Unleashed Rage.
For even better results, I suggest downloading
WF3Sec mod to show you your hidden WindFury timer right next to a StormStrike timer so that you can avoid punching your Stormstrike while your WindFury is still cooling down.
I guarantee you WILL be kicking yourself once you get SS for not taking the talent sooner.
Edited, Sep 25th 2007 4:15pm by Elecktrofreak