My preferred way to code is leaning back in a chair with my legs resting on an ottoman or something similar. I'd be really interested if anyone else has more (anecdotal?) evidence supporting this.

For the record, I tend to develop using a laptop resting on my legs, and my arms at my side, since my desk chair is pretty wide.

I do wonder whether I'm going to regret this in 20 years.

I use a range of postures throughout the day. I spend a lot of time in an armchair in a common area, where I alternate between crossed legs, legs in front, or sometimes legs lying on the short table. I spend some time standing at my (not high enough) desk. The geekdesk looks amazing ... I am going to ask for that next week. I think you can get away with a lot of bad posture stuff if you get out and exercise during the day. I take a 3-4 mile run followed by a workout most days. That keeps me feeling great even when sitting with "bad" posture.

I'm the same when it comes to typing and I've found out that the Aeron is perfect for this. It leans back enough for me to put me legs comfortably in the desk and due to its robust build, I know it won't be breaking in a year.