Yes, they are worth growing. They're an absolute staple in our garden.
Many decades ago my in-laws retired and moved from London to Lacock in Wiltshire. Down the hill from them was a chap who sold surplus veg; we went in one day for some tomatoes and came out with a clump of welsh onions as well. They went all round our garden, and then to the allotment. Loads of plot-holders have had off-sets from them. And now they're coming back to us: ours have been gradually dying, but we're being replenished by our friends. (Isn't that what gardening's all about?)
On a practical note, pick the stems as you would chives, or dig up a clump and use them as spring onions. I couldn't live without them.