That game is playable, though it's about half/half with people who can connect just fine and those who can't. The_Monk wrote a great guide to improve your ability to connect and the recent patches have made it far better as well.
Lan works fine and there are plenty of Hamachi networks hosting games, we're planning on starting a Leaf network as well.
I'd say pick it up, might as well even if you chose to believe the first poster. Shelf it and play it later, but at the very least you should play through some single player matches to get the game down.
If you're a dota player then you should know how important it is to know your hero and not wast time fumbling around with items or builds against others. Else you get people who join online matches, sometimes ranked ones at that, and then ask where to buy equipment..
Yes, it would be far more fun to learn against humans, but you should be able to connect fairly well (I don't have any problems since the last patch, before that it was a crash from time to time and only be able to host custom games and not join custom games). Even if you can, you can be positive and see this as a chance to learn the game, not just the hero you like but heroes others will eventually fight against. Know thy enemy, as Master Sun said.