If it's not cracked, and the braking isn't compromised, I'd keep using it.
We used to straighten dented MTB rims all the time - before disc brakes, this inevitably ended up with a bit of pulsation under brakes, but that's tolerable when you're broke. Road tyre pressures are an added complication (as are road rim weights - I always had a big of spare meat in my cheapy MTB rims), but I wouldn't expect strength to be significantly effected. Especially if you've been able to straighten it enough to achieve good braking... it must have been less damaged than the ones I've rescued
Keep a casual eye on the impact location for any sign of crack growth over time. You'll get plenty of warning before it becomes a problem.