I've been working with a (very good) co-author in the past. He is better than me at some things, and I'm better than him at others, so working together is great and fun. However, because he is good at X, when I work with him, it just usually turns out that I don't get to develop my skills at working on X (simply because he's faster and can get there before me when I'm still stumbling). I guess in the short run this is fine (because the papers come out faster), but it worries me in the long run.
And, because co-authoring is so fun, I don't get to work on things that I personally really like, because the other thing is taking up all my time.
So, is it possible to work with a co-author and develop my skills, without ignoring my own projects?