When I did my A320 course it was my first jet rating having come from piston twins and a bit of turboprop time. I cannot say if it is harder than a rating on a Boeing but I found it relatively straight forward. The hardest (and most time consuming) part for me was trying get some sense out of the manuals (FCOMs). I particularly enjoyed, coming from traditional cockpits, the vast amount of information given to me by the EFIS and FMGS. This coupled with Airbus' flight control system made instrument scanning and what little hand flying we get to do, much simpler than I had expected. All in all a wonderful machine and it is a great rating to have...so if you get a chance to do one, I wouldn't think twice.