Hi Brum,
I use it, from time-to-time. It's traditionally only used in vegetable and dhal dishes.
It adds a quite distinctive smell and taste to the final dish. You really do need to use it sparingly though, in my opinion, but I've seen that some people add half a teaspoon or more.
I use just a pinch (maybe an eigth of a teaspoon) and, as Santa says, add it to the hot oil, and fry it for a few seconds, before adding the other ingredients (i.e. garlic, ginger, spices, tomato paste, curry base, etc).
It stinks of suphur compounds when it's raw ("devil's dung"...actually I quite like it!

) but that changes to a distinctive sweet, oniony, garlicky, smokey smell and flavour when fried.
I've been using Indian "LG" compounded powder (a cream coloured powdered mixture of asafoetida, edible gum and wheat flour) and it seems to work just fine to me. But I haven't tried the resin (mostly because I have never seen it!)