We recently used Execucar and I was a little concerned based on some of the reviews here. But I have to say it was a good experience overall. Our arrival flight changed and we even had to arrive at a different airport - I called Execucar and they cancelled that leg for us and booked a new one, no problem.
The driver was nice enough ... we didn't talk and that was perfectly fine with me. Quick and no problems at all.
On the return, the driver was right on time and again, nice enough although we didn't talk (my preference, tbh). He also knew a back way to get into LAX, which kept us moving and felt like we weren't stuck at any time.
it was exactly what I expected, prompt, efficient and professional. We didn't have any issues and would def use them again.
just my 2 cents.