My eldest dd had a very bad squint, turned right into the corner and upwards as well. We did the patching for years (started just after her second birthday when the squint suddenly became noticeable), but all it did was make her blind as her left eyesight was so poor - covering her 'good' eye all day was actually quite a cruel thing to do to her because she couldn't see. We had several miserable years with her struggling. Great if it works for some, and I'm glad we tried it, but it wasn't the answer for her.
I was the same, as was my dad and several of his siblings, so obviously it is a hereditary thing for us. Eventually, aged 7(ish - can't remember exactly, she's 25 now) she had squint correction surgery, and has had a further two follow up operations, the last one just last year to try to keep her eye as straight as possible.
I've had two operations myself, my left eye has almost no sight, but my right eye has almost perfect vision, so it's possible to drive. I can't play tennis, or anything where you have to judge a ball coming towards you, and 3-d specs are a waste of time for me. I do wear glasses for driving and watching tv, but the prescription is only to sharpen up the sight in my right eye, the left one is plain glass because no prescription will ever help the sight in it.
Only one thing on this thread I would take issue with is the thing about squint correction surgery being only cosmetic. Yes maybe technically so, but having had the confidence knocked out of me, I really did appreciate having the chance to look people in the eyes without feeling self conscious. I remember (post op) my dentist saying to me he hadn't noticed my squint before (because I never used to look straight at anyone) but that having it corrected was the best thing I could have done as my personality changed dramatically afterwards. My dd feels the same. For us having straight eyes was about much more than cosmetic reasons.