It's like a crack dealer giving you the first hit off the pipe on credit at 1/2 price.
It's totally true. When you've never used really nice tools you don't know what you're missing out on. Then you also realized if you're gonna spend a ton on tool-truck tools, you might as well get them from SO cause you know they will still be in business if you're tool breaks and you want to exercise that excellent warranty 20 years from now.
What the guy told us at our school was in the end everything averages out to around half off. I found that mostly true. IIRC the discount is only good for something like $6K, but i'm not sure about the exact number, and i'm not sure about whether that number applies to how much you actually pay, or for the retail value.
Honestly i'd suggest waiting until you're almost done with school to buy stuff from them. That's what i did and it turned out great. It takes quite a while to realize where you really should spend your money, what tools you need SO quality in, etc. I know had i spent the money i did at the very beginning of school rather than the end, i would have probably would ended up with a much worse collection and have spent more.
I think the most important things to buy from SO are things like ratchets, breaker bars, pry bars, pliers, locking impact extensions. The kind of things you use the most, and the kinds of things where the extra quality makes a very large, noticeable difference.