I have an opportunity to buy a second hand spinnaker sock.

Are they worth having?

I'm not ready to fly my kite yet. Still lots to learn.
My boat came with 3 spinakkers, so I will one day.
So thought it would be a good addition to my sails.
Thanks

G'day BJ,
Unsure if you are symmetrical or aso, but I have a sock for my aso. I find it really good for cruising and short handed work, racing not so much.
The main issue with racing is you tend to have the headsail out when you want to snuff or launch (you don't want to sacrifice any speed) and it can be difficult to work the snuffer when you need to be on the lee side of the headsail.
When the headsail is out of the way, it's a cinch, my aso is 155m2. I blow the tack line, stand in the middle of the foredeck and snuff away. Gybing is a bit of a two stage thing, turn the boat, get it settled, then go forrard, toss it around the forestay, then launch away.
I like it, but they're not for everyone. Hope this helps.

Can you pack it away with the spinnaker in it?

I pack my aso away inside the sock, no problems.
I raise the sock directly from the bag thru the front hatch, just make sure the head is at the top of the bag when you pack it away.
Once the sock is up secure the halyard and then clip on the tack and sheet. When you are ready to deploy raise the sock.

If it's wet you will need to dry before packing away.
I've dried my over a few days inside the cabin by pulling the sock up and spreading the kite out.
Eaiser to dry it at home if you have the space