I generally get the cheapest programmable Harmonies. Why buy a $250 rechargable remote with annoying touch screen when you can get a Harmony 650 for $50 on sale? It's not as if the rechargeable one actually controls your devices any better. The main limitation of the 650 is the number of devices supported. (Actually if you're transferring from another Harmony remote that isn't an issue either, because you can transfer all your programmed devices over, regardless of the device number limitation. The device number limitation is an artificial marketing one, not a technical one.)
And yes, you can program the buttons how you like. The 650 as 4 coloured buttons that don't do anything normally. My PVR has ABC buttons which don't have corresponding hard buttons, so I have programmed the first 3 coloured buttons to be A, B, and C.