I've used vim for so long that I don't find hitting the escape key to be a bother -- in fact, I don't even notice it at all anymore. It's the same with hitting :

It would take much more effort for me to retrain myself to use control-[ or some other key than to keep using escape.

On the other hand, if I was just starting out, I might consider remapping jj or jk to escape.

I've already mapped the space bar to : but I keep forgetting to use it. It's all muscle memory at this point, and a bother to retrain it.