If the developers implemented any more interesting mechanics that let you rewind time, or made some enemies immune from time pausing then this might become an interesting game, but based on the demo it just looks like a shallow but pretty game, and is unlikely to be that much fun.
That's an interesting question - once you can nail every headshot, plan every evasion, and spot every foe with complete ease... is an FPS still fun? Can it be made to be fun?
Obviously, for an FPS fan for whom the skill is a core part of the gameplay, this might not be an interesting question for them.
I think this title could benefit from something similar. It's a fine line to walk though, they have to be different enough to not just be a rehash.
The game most definitely turned into a puzzle in the same way that Braid's levels were puzzles. I can't see how you could say it was anything else.
IMO, the demo was a blast. If they made 30 more levels like the demo, I'd buy it. Adding grenades, swords, and interesting level designs is more than enough to warrant a purchase.
Just moving around in the prototype is a lot of fun, and that can go a long way for me.
I'd really suggest playing the demo they put out. I'm very excited to see a full game come out.
And just at that point the story took some turns and I was hooked. Amazing game, and I can't imagine the amount of tweaking involved to get the balance just right.
It is worth replaying with the "commentary track" option afterwards: it is quite an education to find out how much play testing and rework effort goes into trying to get everything "balanced just right" even for a game of that size (which in turn explains where a chunk of the massive amounts of money and other resource ploughed into some larger titles goes, and why naively cheap game based kickstarters are a often bad idea).
If with this game the creators can wrap the other elements around their core gameplay artifact(s) in the same way then it'll be well worth a go, if they can't then, well, that is always the risk of kickstarter and it is your choice (valid either way) to, or not to, take a punt on that.
I am intrigued by this commentary track, looks like I'll be playing Portal tonight!
There are various bits of the commentary when they discuss previous versions of levels and why they changed things after the play-testing sessions. A lot more effort seems to have been expended getting things as close to "just right" as possible than you might first think.