We've have the AeroCut Pro for about 4 years now (the version before the X was added to the name). It's mostly the same machine with just a few modifications. We do thousands of business cards each day, along with other various cutting/creasing/perfing operations for custom jobs.
We've been mostly happy with it. We have not had the feeding and cutting consistency issues others have described. It is very easy to do user maintenance because every component either slides out, or has 2 thumb screws. However, there are some things we don't like with this older version that I know have been added to the newer X model such as:
1. an output tray setup mode
2. fingers to keep the business cards from flying out
3. A larger, more intuitive touch screen
4. A waste conveyor.
However, two things we really don't like have not been updated:
1. the slitters automatically have a 7mm gutter. This means you can not do chop cuts.
2. On the feeding end, there is a magnetic side guide that you must manually align. This allows for user error to make it too tight, or place it at an angle, causing the paper to feed incorrectly. It's not a problem for our more experienced users, but the newer guys struggle with it. On the Duplo's it's a sliding bar that always keeps the paper straight.
Lastly, if you use a Fiery, the Duplo is a better option because the templates you build can be shared between the devices.