Richard, I agree the Power Cab is very good. Upgradable too and it can work with the higher end systems.
I think that what the Dynamis has to offer is fine for most people who are starting out in DCC. The one or two "faults" that people are talking about are solved by the Pro upgrade due out later. All in all, a well rounded system. I'd just like to see it running a large layout and see if it is better that a Lenz system which I regard a a good benchmark to match up to.
If I was using the stock Dynamis, I would wire up a programming track all the same with a few DPDT switches so as to prevent the need to take off all other locos off the main track whilst programming.