In July we took the Disneyland Express from LAX to DLH. The also service SNA but I have never personally used SNA.
We were very pleased with them. Their first stop is the DLH, were we got off, so I'm not sure how many stops are between DLH and DGC but I'm sure there aren't many. There weren't even that many people on our bus to begin with and the was during busy season and at LAX.
If you do use them, make sure you go to the web site sometimes they have coupons for discounts.
Southern California Gray Line - Airport Information