Just rented this past weekend from LAX as a Platinum.
the office is in the front corner of the Renaissance hotel, you have to hunt down for it a bit.
They were offering cash upgrades to a BMW 428 convt for $15 a day, and was able to get it for free as a Platinum (or since I was booked into a premium category for a Cadillac ATS). Staff was helpful and pleasant.
For a BMW AI at $120 or so for a weekend, where Hertz was $100 for a standard fullsize, I'm excited that Sixt is finally at LAX.
Be aware though that they use the hotel shuttle to get to the terminal (15-25 min wait). Only downside to renting here vs Hertz who has their constant shuttles.