I certainly feel like I can bolt out of my boat, undo a biner and throw a rope while wearing the Reactors ... As for more complex stuff, yeah I could see a problem. That said, if your hands go numb from cold, your fingers won't be working too well to do intricate things anyway, yeah?
If I get out of my boat to scout and set safety when it's cold, it sure is nice not to have pogies. It seems when you have pogies, when you get out to scout/set safety, your hands get colder b/c they're exposed. But with the Reactors, when you get out, your hands only get warmer because they're still in the gloves but no longer in the water.
That said, for long periods of uninterrupted paddling in serious cold, pogies are warmer, at least while you're wearing them.
Also, with the Reactors, they will fall apart. They'll come undone at the seams between the thumb and the pointer finger. The stitching comes out. Every time. I've had like four pairs, and they all do it. I probably get about 30 river days out of a pair of reactors.
I've never been bothered by the finger curve -- that shouldn't be a problem if the gloves fit you.
I have both pogies and Reactors, and use one or the other depending on the situation.