I've never seen a plane that couldn't take off just because of too much power. I have seen planes that are overpowered that have snapped in on takeoff, but it's usually caused by #1, operator error, #2 too much weight, and #3 the CG too far forward. From the landing side, if you have too much power and the wrong prop, the plane may not want to slow down enough to land, but this can usally be corrected by decreasing pitch, increasing diameter and proper low end tuning (or just killing the motor on final). Given the right equipment & design, 2-3:1 T/W is doable, and can fly very well, but it does typically take some throttle control to prevent damage. 1.5:1 seems to be about right for good areobatic performance, and 2+:1 is required for any serious 3D. I've played with thrust to weight, theroretical top speed, measured in air RPM & speed, etc. and after all that, nothing beats grabbing a handful of different props and flying them to find the one that works best.