Hello,
I have the
nautilus coming in the mail as well. From what I understand, just follow the manual. Also, start at 3.3 volts and work your way up.
I have had my ProVari since August of 2012 and NO PROBLEMS! I've even dropped it on the asphalt a couple of times. One time, a carto broke off at the threads and I had to use my Leatherman to get them out of the ProVari. No big deal...
Make sure you do the weekly maintenance and stretch the spring when the battery volts start dropping off prematurely or just change the spring every 6 months if you don't want to stretch it.
While I have no experience with the Nautilus, I know the ProVari will make you VERY happy! 1 1/2 years and it has NEVER failed me!