Absolutely! We can use all the Gildar we can get!!! Especially in the early game!!!
I never sell it though, it has sentimental value (I keep thinking I'll need it for some other quest down the road or something). I had to talk myself into selling the flute, but since we can't drink the flute anymore...
Someone will introduce another quest for that key and the flute at some point, I'm sure of it!
I always loved drinking that flute 
Well you can always equip the key to your char, althought no change on stats it will stop appearing for sale ^^