I can relate to anyone who's geometrically bothered by the 1:1 move rule. I thought it was unnecessary and excessive simplification, did not believe the "it's faster" arguments, and thought it would cause so much glaring weirdness it would be impossible not to notice and get used to.
I participated in debates, mainly on Wizard's forums. With other posters I did lots of maths, not so much because this 1:1 vs. 1:1.5 thing is serious buisness, but because I like doing math, and defended it. Because I make it a point to always allow for the possibility that I may be wrong in any debate I participate in, I said I would try 1:1 before deciding if we should go back to 1:1.5. Can't base a whole argument on science* without doing all the science, and that includes the experimentation.
And now that we've tried it?
1) We did not notice the weirdness;
2) In the various maps we've had fights on, we almost never did any long diagonal moves, the kind of moves that would have had the largest error vs. 1:1.5 or correct euclidian movement;
3) It did speed up play a bit because there's never any recount. I can't say how much time is gained, though, as other changes from 3.5e to 4e also contributes to the speed-up;
4) No one had problems adapting;
I don't think 1:1 is better, but it's disadvantages are far less than I had anticipated, so small in fact as to be unnoticeable. Now I think it's not an issue worth losing any sleep over. I might change my mind again as we start using large AoE attacks that are too obviously square, but for now, 1:1 is fine.
So, I suggest you give it a try before deciding, like I and many here have done. Right now, you're convinced it's a stupid rule, and I completely understand you. Try it, and then you'll know, one way or the other.
*Can you believe it? "The science of D&D movement." That sounds so silly now.