I did a high-altitude training stint last year and it was a game-changer for me. The biggest difference I noticed was in my mental toughness - being pushed out of my comfort zone helped me build confidence. Physically, I saw improvements in my lactate threshold and overall endurance. When I returned to sea level, I felt like I could hold a faster pace with less effort. It's not cheap, but if you can swing it, I think it's worth the investment.
I'm with you on prevention. I've found that incorporating strength training and stretching into my routine has really helped reduce my runner's knee issues. Consistency is key though!