Excerpt from Recipe Journal: Potato Salad

It's the wrong time of year, but I don't care - I think I'll eat this year round. The thing about potato salad is that I don't like it, except that I love the potato salad from Steven's Market Deli. I ordered it by accident - I thought it was German potato salad (which I do, indeed love, but Steven's doesn't carry it anymore), but went ahead and tried it and was amazing. So my thought is... can I make a better potato salad?
We watched Cook's Country and they made ranch potato salad which sound good but not like Steven's  - however Steven's potatoes, though cooked perfectly, don't in themselves taste like anything - so I'll try the method of adding vinegar and dijon mustard to the hot potatoes, a la the Cook's Country recipe... and then what?
Celery cut the right size is key and I'm expecting everyone has their idea of what the correct size is. Steven's adds carrots, but they are the little pre-cut ones - kinds of grated pieces - so they are dried out, which is good in a way. There is boiled egg which I like in small quantities. What I can't really tell is what they use as a binding agent. I want to figure it out and not ask Steven. It's creamy but doesn't seem like mayo, but it's not sour cream. So what the heck is it?
One of the things I love about Steven's is the fresh dill - yum - just enough to be perfect... but how much is that? Experimentation is in order - @ least when I stop buying from Steven's (never).