Re: Invoker = lame, annoying and easy hero.
Whoops, wrote a fairly big post then lost it. Oh well. Basically, came down to this:
Invoker's got an easy early game with free tangos/easy last hitting, easy early/mid game with great mobility and escape mechanisms when ganks start happening, easy mid/late game with powerful and relatively easy to use spells. Choosing what spells to use isn't hard - use your spells that you have points in earlier on (about 3-4), and then use everything when you've got Scepter and the mana later on.
Invoker's spells are not that hard to use. They've got fantastic range/AoE/damage, and there are fairly simple combos to make the somewhat harder to land spells, land. (EMP, Ice Wall, Meteor etc.) Even if you miss a Cold Snap or Tornado or something, you still have many spells in reserve. There is no "ult" you can miss, no Black Hole you have to obsess over landing properly and not getting interrupted, no positioning at a crucial moment to worry much about.
Disclaimer: I am about 60-30 with Invoker, and love playing him. I just feel a little guilty that he's a bit of a pub-stompy hero that isn't that difficult to play once you get past the mechanical barrier-of-entry.