AR will work fine. IMO, Remote Master software does make the AR much better. It's hard to beat getting $150 worth of remote technology for under $20.

The main complaint about the Ultimate is the fact that it's a touch screen - a feature you actually want, so that will work fine too. People upgrading from older Harmony models miss the hard buttons that you want to avoid.

iPad works with iRule or Roomie and a Global Cache base for the IR portion, so no IR LED to plug into the iPad itself.

With only 4 devices, I think an iPad and even an Ultimate is huge overkill. A Harmony 650 will do the job, if you can tolerate having some hard buttons.