I think the OP will be fine. The 405 only has one sizable hill (going into and out of the San Fernando Valley), otherwise it is relatively flat. We have had our REx for a bit over 2 months now and I have purposely run out of charge in various situations to see how it performs. I now have...
We just installed a Siemens VC30GRYU Versicharge last week for our 2 week old Rex. Works as advertised with no issues at all. We purchased it through Amazon. Picking out which charger was more difficult than getting the i3 :)
Just picked ours up this past Saturday...
MSRP 51245 (Rex, white, giga, tech)
Down: $2500 (basically $0 when we get our California rebate)
Term: 30 Months
Payment: $285/mo