A couple of the major issues with SaaS products like Practice Fusion (to pick a popular example) may be minimized or eliminated by AC's version. Owning an up to date version of your database and keeping it in your own office is major. It reduces the impact of internet outages and guarantees that you have access to your records in the event of a termination of your relationship with AC, for whatever reason. In addition, while Practice Fusion reserves the right to sell your data; and in fact is widely believed to do so- hopefully AC will not ask for that right, and can be trusted not to exercise it. You would still control your data.
This eliminates several of the most serious reservations that I would have about a SaaS product. It does not mean that I will sign up (I have no intention of doing so) but it does mean that I would recommend it as an option to those who are interested. As Alan and others point out, many docs prefer the option of a hosted version that frees them from many IT responsibilities.
