No catches. It really is simple and you can copy all info over to the second POA with a click of the mouse. Plus the software automatically crosses out sections that aren't applicable (for example if you have only one attorney). You can also save the document at any point and go back to it later. You still have to print it and get it signed and dated, but at least no one can mistake your handwriting for a different meaning! I also thought it was easier to fill in page by page instead of overloading you with guidance notes like the paper version.
I did mum's on-line. Whilst long-winded the forms aren't complex so unless you've got a particularly complex arrangement you should be fine to do them yourself. Another example of solicitors charging a huge amount for what is something pretty straightforward!