You can get strings, picks, etc. at dozens of places both locally and online, so why Strings and Beyond? My answer is that, beyond their great selection and good prices, it's like going back in time 50 years and dealing with the friendliest, most helpful neighborhood store you can remember -- or imagine, if you weren't around back then.
Every order I've placed with Strings and Beyond has come with a handwritten thank-you on the receipt. I had a 20-minute online exchange with a very knowledgeable support person when I was looking for the perfect thumbpick for my playing style.
It's not World Peace, but I would be a very happy man if every company I dealt with was like Strings and Beyond. They are a rare find.