A flag register is indeed an additional dependency and may end up in the critical path. But x86 and ARM already have a flag register. They already pay the cost.

And you don't need a flag resister to check for overflows. Trap on overflow (like Alpha) will work just as well. The difference is that traps are infrequent so you don't have to make them fast, just correct. You don't have to raise the trap in the same cycle that you calculate the integer operation. You just have to to do it before the commit stage. (And the last time I checked, the Alphas were quite a bit faster than MIPS.)

Of course hardware support implies some overhead and more complexity. I can see why people would oppose it. But there really is software that would greatly benefit from hardware support.