Multiple points of entry. If you don't want to spend actual, physical cash on the game, you absolutely do not have to. I've only spent about $15 on the game. That being said, if you're starting this late, you should spend a little bit of money so that you don't get too far behind what's going on. That being said, you don't have to spend a ton of cash to be able to do so - I know plenty of people who have started later on and paid $40. Then, there are lots of ways that you can earn packs and extra cards to get to where you need to go, and you can craft cards using dust from cards you don't need and/or have triples or more of. The multiple ways that you can get cards makes it easier for you to get to a competitive point.
The internet is the next frontier of CCG's. Even though I'm someone who loves face to face interaction when it comes to board and card games, I do think that they will, at some point, be overtaken by online CCG's like Hearthstone. If nothing else, I think that the mass appeal and mass popularity of Hearthstone, even before it went live, is what shows this fact. Do I think that the standard CCG's will still exist? Absolutely. But they won't be as popular as the stuff you play online.
People know how to chill the heck out. This is one thing I like about the Hearthstone community. I mean, yes, I am totally certain on the fact that there are some people who act like total and complete jerks in the HS community - but those people are pretty much everywhere that you go and play games. Trust me, I've been in CCG communities - some of them are incredibly toxic, and it's sad. Anyway, it is really a good community in the areas that I've been in. Sure, people are jerks at times, but I think it's at a better place than a lot of CCG communities, especially when you're looking at the top end of them.
I know that Hearthstone isn't perfect - there's rarely a game that can meet that standard - but it's important to at least note and realize that it does a lot of things right, which is why it has become such a popular game in the time that it's been out. I've been playing since the beta, and I'm really glad that I got into it early. I'm definitely not the best at the game, but I do know a lot of what's going on with it, so that makes it a fun and engaging experience. I definitely recommend that you try it out if you like CCG's at all.