The flight to SBA that arrives/departs midday seems to be doing well. From my flights there and talking/overhearing conversations, it seems like is generating business from pax going to/from Simi Valley that are avoiding driving into LA airports and pax visiting wine country up in Paso Robles. The late night/early morning flight seems to be struggling though, which makes sense given that you are not going to want to drive to SBA to catch a 6am flight or arrive at midnight when the rental car center is closed or drive to your destination at midnight. I would not be surprised if they decided to scrap the second SBA/SLC flight (or at least downgauge it to a regional jet) in favor of an SEA-SBA or MSP-SBA flight that arrives about the same time as the ATL flight and departs about the same time as the ATL flight in the morning.

A flight to SBP would cannibalize some of the traffic and I would not expect to see that happen until the SBA route is better established. SBP is crazy expensive to fly into from here in SEA so I would not be surprised if Delta tried SLC-SBP, MSP-SBP and/or SEA-SBP in a few years.