Okay, I have to admit at the start of this "review", I have pretty much no interest in bridge construction games. I am playing this entirely because they slapped the Portal franchise onto it. I enjoyed the two Portals immensely (and I'm obviously not alone) and so any chance for a bit more of the style is going to grab me.
The original games were rather groundbreaking, making use of the Portal system to add an element to puzzle games that had not been done before, and that's added now to the bridge construction genre. That's not quite as revolutionary as you might expect, mostly resulting in a few flings around the screen with a less linear path than might otherwise be required.
It does throw in various other aspects, such as turrets, faith plates, lasers and so forth, but you've still got to sit building a bridge, which is far less interesting to me than it might be to others.
At least you can have a bit of a laugh causing mayhem.
I'm sure people who enjoy construction games will enjoy this one. For them, the Portal aspect may prove a nice added bonus rather than the reason to turn up. For me, someone who is here mostly for the Portal, which includes the fun little animations and GLADOS being horrible, you're fighting the game to get to the cutscenes.
If you're interested because it's Portal, just watch a Let's Play. And to be fair, the Portal aspects are really enjoyable. They've got a niche, and they fill it well. But this could have been a short film. If you're a bridge construction nut, have at it.