Storm mixes pretty good with most things. I haven't played it, but off the top of my head I don't see any huge conflicts. Having Hurricane on while you are trying to use Hail of Bullets is likely to be problematic, and letting the Tornado run free while you're setting up your AOE's could be annoying too, but those problems are pretty consistent in the defender version of Storm regardless of your secondary.
I say go for it.
"Good" and "playable" are often subjective words. What you would consider to be good may or may not match someone else's defintion, so specific questions are more useful (i.e. "how well could this solo?" or "how well does this pair with X?").
Storm Summoning / Dual Pistols is indeed good and playble. At least, I think so.
Iscariot's Guide to the Tri-Form Warshade, version 2.1
I'm sorry that math > your paranoid delusions, but them's the breaks -- Nethergoat
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there is some discussion of Storm/DP here
Draggynn on Virtue: lvl 50 Storm/Psi, 1389 badges
Draggynn's Guide to Storm Summoning(Gale-Tornado, updated 6/25/2011)
Avatar by Wassy full reference here
A friend has a character concept which, purely conceptually, would be AWESOME as storm/DP.
Is that a good/playable combo?