Most of the community is pretty good but unfortunately whining in this game is pretty common place and across the MOBA scene as a whole -> "Always some one else fault".
The more games you play hopefully you'll move up the ladder a bit and hopefully those kind of players wont be as common.
While I wouldn't consider my self a 'pro' by any means I have some considerable amount of experience with MOBA games. DOTA2 at the moment has a balance issue with the characters current available, a great example would be Anti-mage.
At the moment I see a lot of complaining and calling him 'over-powered', while there is a patch this coming week to tweak his armour to 1, the main issue is the heroes that hard counter him such as Obsidian destroyer and Invoker are not in the game yet. I'am under the belief that Spirit Breaker and Silencer will be in the patch this week, this will go some way to containing him.
People discussing Spectre dominating teams past the 40+ minute mark this is due to her being "THE" hard carry of dota. If you watch any pro-games with a Spectre in; you may at times here the commentators talk about the "countdown" as pros often call it. This is the time it takes for a spectre to get a Vanguard and her ganking/farming should go through the roof.
The first 20 minutes in a Spectre game is crucial for the opposing team, you need to really sit on her and strangle the gold supply. A recent interview I will try to source had a Meet Your Makers player say that if your not considerably in-front of the opposing team with a Spectre in it by the 40 minute mark its practically over. A farmed Spectre is devastating as are most carry s but getting a Spectre to that point takes some considerable knowledge and at lower games some luck.
If I was to recommend a hero to begin with it would be Lich, a hero which does not require a good amount of farm to stay relevant all game. Has a devastating ultimate move and can regen/deny fairly easily.
A channel you may find useful is Purge gamers Youtube channel:
http://www.youtube.com/user/PurgeGamers
A very good player who plays a match with each hero and explains the basics and advanced plays behind each hero as well as items to choose and other information.
As all the hero's are direct ports with the odd number tweak PlayDota has a guides site which you can use to get a over-view and thoughts on a hero:
http://www.playdota.com/guides
Other guide/news sites:
(guides)
http://www.dotafire.com/
(Dota news, vods and commentary - Run by Tobi-Wan (huge dota commentator)
http://www.joindota.com/en/start
Will be a live streamed game starting at 3pm(10/1/2010) for anyone interested:
http://www.joindota.com/en/broadcasts/419-the-defense-group-stage-playoff