Hard in which way? My time at the regionals was some of the most fun I ever had, but my difficulties were centered around crew interactions every once in a while or holding my tongue in front of a passenger which I often failed to do.
20 years of flying a CRJ doesn't prepare you for international charter work, going to places that a typical DL/UA/AA pilot will never see. There's a ton more to learn. However, learning that stuff isn't the issue. I can tell you at 39, I am no where near as sharp as I was when I was in flight school, or even a newhire at Mesa. My experience helps make up for where my brain is starting to fail me, and it ****es me off.