Just finished with DMV this morning - here's how it went:
We completed a SMOG test, and collected all the paperwork that i25 sent to us via FedEx. As part of the paperwork with i25, we had already filled out REG 343. They sent that back to us along with Colorado title/Registration, copy of our Purchase Agreement. We also brought paperwork from the Auto Transport with date of delivery to us, Proof of Insurance, as well as SMOG certificate. We paid cash to i25 for just the car, no CA taxes.
DMV experience - total time at DMV was between 1 & 1.5 hours.
It is annoyingly difficult to schedule DMV appointment on-line - I couldn't figure out on DMV website how to book for out-of-state vehicle registration, so I called to book appointment. At least they have a new "call back" feature, so you don't have to listen to the hold music for a long time.
We arrived just in time for our 10am appt - had to wait in line to check-in, and then were informed we needed to get the vehicle inspection first. So we drove the car over to the waiting area (near where Drivers tests are administered) - waited about 10min until someone came out to inspect. She filled out "Verification of Vehicle" form (REG 31). Needed to show her our Colorado Registration form (which i25 sent us).
Went back to check-in line, and were given a wait number. I'd say we waited about 20min - not sure if we had just arrived about 20min ahead of our Appt and went to get in line for Vehicle Inspection if it would have gone faster? At the counter they only really looked at the form 343, Colorado Title, Purchase agreement etc. Didn't need to see SMOG, Auto Transport paperwork or Insurance. They took our Title/343 form, we paid our CA registration & CA sales tax. Paid via check - as they charge 2.3% fee for credit card and debit/ATM cards. Got our plates & tags, and CA Title will be mailed in about 30 days.
Done!