What a decision. I like the guys over at Impulse a lot, but Steam is where 75% of my games are.
The question is will the Steam version have achievements or not. With them using Steamworks you'd think so.

yay steam!
Stardock's nice, but i like keeping things all in one place...

they will.

Then I should probably get it for Impulse so I don't waste my life trying to get a "wasting my life getting achievements that don't even mean anything" achievement.

I played through the whole game and it was the best puzzle game of the year for me. They are truly unique puzzles that will keep you thinking. I dare someone to find all the secret stars without looking them up. I would agree it is overpriced though, there is not that much replayability.

ROTFL. Impulse is a trash client.
Buggy POS that has no business being put on the same level as Steam.
At least with Steam I have fast archiving of games and easy restoration. With Impulse I had to do manual unarchives and manual installs because the client would not properly send my handle to the 7za program. The archives are passworded with the handle you use to log on to the service.
I had to unarchive the backup manually and then rearchive it manually without the password to get the stupid program to properly restore the game through the interface. That's a big fail and have never had to do such a ridiculous and convoluted process with Steam to restore my backups.
That's not to say that Steam is perfect, but it's sure a hell of a lot better than Impulse.
And their support is next to useless as well. Not to mention all of the issues people have had with corrupt downloads on with Impulse. People having to do ridiculous crap like meddling with files to get a proper download. When I click on something I expect it to work and not have to dig behind it to make it work.

they give you the achievements just for playing the game. you guys have really whacked out ideas as to what achievements are and how they're supposed to work.

This is a bit OT, but how did you manually unarchive the 7z? I cannot for the life of me figure out what password to use. I'm having the same problem you were.
I support both Stardock, Steam, and GOG where I can, because I support both digitial game distribution and competition. I am more sensitive about how the company behaves than how crappy their client is - so I won't be giving any of my money to Fileplanet/D2D or EA.
I think I will be buying Braid through Impulse. I'm on the road a lot and occasionally Steam just decides it's not cool for me to be in offline mode any more.

Ill agree that the backupfeature could use a little work. but for downloads, steam updates, they cap out at 250 kbs, Impulse Ive seen 650+ kbs, and corupted downloads? i have yet to have one. And i have a tendency for reinstalling my OS quite a bit. (tweaking in registry aint wise, even when you know what you do). so i have had quite a bit of experience whit the downloads.

But usually they throw in about 10 that require doing ridiculous stuff, like beat the game in a three hours. And for us completists it's best if they simply aren't there.

Nope, none of that in Braid.

You know you don't have to complete all achievements, don't you? I mean... they are optional...

I've downloaded from Steam with over 1Mbps constantly when I was back home and around 500kbps from here (the networks in the UK suck in the most terrible way).

Apart from the rather difficult time trial one that is (at least its on the 360, I assume the achievements will be the same on each platform)