Shuttle is shared with Ren LAX - not sure if they have a similar offer.
As noted half hour frequency is pretty bad especially considering congestion at LAX, This is particularly unpleasant of you fly on UA/AS etc from terminal 6-7 as you end up waiting for shuttles and then sit in loop traffic on the way out (risking missing your flight) and then shuttles are often packed on the way back towards the end so you have to wait longer.
In general i prefer dedicated parking facilities with frequent shuttles (and from some like park and fly you can easily walk)