Go with the .6 hp motor. That way you have the overhead when you need it and less of a chance to stall the motor out if you get the blades too close. (granted that is not a good thing either but stalled motor when you turn the power switch off draws a huge arc across it, causes it to wear out very quickly). You just want the robustness in the motor. Id like the .8 but now were talking more weight and significantly more cost. I think the .6 will work fine.
Ditch the tamper.
The plastic chute on top. Personally i really don't like it, I mean its like. you just paid several hundred dollars for an awesome grinder, hand made, custom this, custom that, the container for the ground up grounds is .. looks professional, and here you have this cheap piece of crap plastic on the top of it. To me, it really detracts from the beauty of the machine. But what else is there, unless you have a thicker better grade of plastic and not some cheap high speed shot ABS. Maybe some design in the plastic or lexan or a better grade of plastic, a deeper color. You don't really want any ripples or groovings in it because thats a bugger to clean especially when it gets oily from one of Tex's roasts.
As for the speed, slower is better, burr size, I do not know enough about that to be really speaking out on it, but would assume bigger is better (but on that more surface area takes more power to run it hence the bigger motor)
I would say add a reverse switch in case you do jam it somehow you can try the reverse run to try to unjam it... or is that not really an issue with coffee grinders?
It does look nice though.
Aaron
Let me edit and add: Concur on cutting down the hopper on top, you don't need to be storing 5 lbs of beans on top of the thing. Probably a quarter of that size would be plenty sufficient.