I have, yes. It is a good introduction. What I found, though, is that there are some... differences. Like, for instance, I bought it because I was joining a HERO game with a bunch of LOOOOOOONG time HERO-heads. The Basic book seemed like a good place to start - because I wasn't going to buy the set of encyclopedias which are the full HERO rules - and I created a character. Of course, the character had powers, and some of those powers had drawbacks. So, I created the powers using what was in the Basic book. But when the GM and the other players looked it over, I was... assaulted (LOL) with questions of "why did you do it this way?" "why didn't you do it this way?" "you're supposed to do that this way", and so on and so forth.
It turns out that in making it basic, they've introduced differences... simplifying things and the like.
So, if you want to get into HERO, and you want to give the Basic Rulebook a try, I would say GO FOR IT. It's a fun system if you like crunch and math and mechanics. But if you're going to play with the Basic rules, play with the Basic rules; don't integrate the Basic rules into a full rules game, unless the GM is willing to apply some handwavium and accept the differences, or someone is willing to do a few character updates to bring your character up to par with the full rules.
I hope that makes sense. :)