I've had my cab for exactly one month now (first one delivered in Orange County) and have loved every minute of it! Unfortunately, right now it is in the MBZ/smart repair shop in Laguna Niguel.
Last Thursday, the SRS (airbag) light came on (about 750 miles) Mark Derengowski, smart center GM (a great guy) said this was the first one to have this issue.
I just spoke to the assistant service manager and he indicated that it is a seat belt sensor and that they can't release the car until it is replaced (for safety reasons). The replacement belt needs to be sent over from France....best case, a couple of days, worst case a couple of weeks.
The service guy said he had calls on two more yesterday.
My advice if your SRS light comes on is to call smart service, let them know so they can order the seat belt BEFORE you take your car in.