Just want to know if they all take aprox. the same time to "beat"

No, unfortunately the chapters get shorter.

Chapter 2 is about the same size as chapter 1, but chapter 3 is much shorter. For me, it took about 10 hours to beat chapter 1, perhaps 8 or 9 for chapter 2, and around 3 for chapter 3.

Part of that, though, is that as your character gets stronger, combat is easier and i died much less than in the beginning.

What the hell, that makes the game very short! They were saying it was 40 hours for the main storyline and if you did the sidequests, it could be over 100! Did they just lie to us?

In a word, yes.
There is absolutely no way you could ever spend 60 hours on the sidequest, considering there are no that many and they're pretty short (and most of them are boring as well imo).

You could spend 40 hours on the main quest, I suppose, if you play really slowly and are bad at fighting.
Or maybe they're counting the fact that following a decision in chapter 1, there are two paths through the game (well, mostly two quite different chapter 2 stories). If you want the full game you'll have to either play through twice or reload a save from before the chapter 1 choice. Still, a single playthrough is much shorter than advertised.

They said 40 hours for just the mainstory, I doubt you could spend 40 hours on just the mainstory without sidequest unless dying at every single monster and reloading.

I think they said that if you do the main and side quests it would be 40 hrs, and another 10-20 hours of replay due to the decision.

The Witcher ‎@Sarvesh: we're estimating around 40h playthrough for main storyline. But that SHOULD be doubled or tippled... for the non-linearity. :)
That is a quote from the rep from cdprojekt during the qa session with gamestop a few days before release.
You can find the whole thing here
http://www.facebook.com/GameStop/posts/183259955056946

Well that's an outright lie, since the "nonlinearity" is pretty nonexistent outside of that one choice, and that definitely doesn't amount to double the playtime.
Still, lies from PR people are nothing new; it's almost in their job description.