OTR added checkpoints and a new area, I would guess it is the way to go. They're the same game at heart.

If I have DR2 do I want OTR for 9-ish bucks?

If you really like DR2. I'm considering it myself, it's $7.50 on its own. Not having checkpoints was one of my biggest issues with DR2 so it feels almost worth it for that.

Anno 1404 Gold is for $5 on GMG. Anyone knows why this isn't avaible on steam?

Ubisoft refused to provide a critical patch.

And this is the reason why this isn't avaible on Ubishop too? Well...

I have only the base game, retail. I would buy Anno 1404 Gold on steam if possible. Btw. what's the critical bug, then?

In the GamersGate Email they say SoulReaver MIDweek, so I guess Friday.
About Steam, it`s bite or die.
You won't get to play DX:HR any other way. Well, maybe in 10 years when it comes to GOG ;)

Some games you should NOT get on Steam like Batman Arkham City or Max Payne 3 because the have an additinal 3rd Party DRM and activation limit. So if you run out of activation and want to buy it new you need an new account, since Steam will NEVER remove a game-license from you library. While GamersGate will provide you with a new serial key, since it only uses the original DRM.
Just some thoughts.

PS:
Today on GamersGate is War of the Human Tanks Deluxe (incl. Soundtrack) for €$3.

And for our Adventure Gamers:

Knights in Shining Armor: Our King's Tale Episode 1 for €$2.04
for the price it seems ok.

Reversion Meeting is 50% off €2.49 and on Desura. Sounds like Momento turned into a game.

Also SpyLeak if 50% off for €1.

Until Thursday, 8:00 am GMT.

Yes, it did not say weeklong but MidWeek sale. corrected that :)

Also there are some nice indiegala Sales:

Hamlet is $2 ($1 with Galapoints!), Steam
and the
The AquaNox Bundle
$2 for Genesis Rising and $4 incl Aquanox 1 and 2, all Steam.
Runs for another day.

Eat My Dust Racing Bundle

http://indiebundle.org/racing-bundle/

The three games offered look pretty good even if not Flat Out quality.

I probably missed the discussion on this, but: How does Steam support react when you ask for additional activations?

I'd be interested to hear this, as well. The deal looks great, but I don't want to bother with GMG stuff.

It took a bit of research just now (I have a hard copy) but apparently when UPlay was introduced Ubi did the cheeky thing that EA did and proceeded to continue patching all versions of 1404 with exception of Steam's.
Look above - If you have a non-Steam copy I don't think you have to worry.

So, seems like ArmA 3 is going the alpha funding way.
Store
The alpha is currently available for €24.99/$32.99/£19.99 and is available until the beta comes out (Q2 2013).

So it's about half price, if you already know you want the game.

They tell you to ask the publisher, they only sell the game they don't support it. Steam likes to claim they're a service when it suits them and then a simple seller when it suits them.

Steam does not provide add. activations because they have no control over the 3rd party DRM. eg. Games4Windows Live, Gameshield, ACT, SecuRom, whatever.
Pure Steam DRM itself, doesn't limit the number of installs or on how many different computers you install, as long as only 1 instance of the is running at a time. (of course in Offline mode you could run several copies as long as they don`t use any online features)
You CAN try to appeal to the original Developer/Publisher to reset your activation count.
MOST of the time Steam mentions the use of 3rd Party DRM on their page but sometimes they don't.
There was quite some upheaval recently with "Of Orcs and Man" which was hiding the use of a draconic 3rd Party DRM on Steam.
One can never be too careful, these days.

But in your case DX:HR is safe and 99.5% of the other games on Steam also.