Just spent 7 days in ZIH - Ixtapa, we were there from March 25th - April 1st 2006.
I was pleasantly surprised at the diving there. We wanted to dive with Carlos Scuba, but he was booked up. He recommended Ixtapa Aqua Paradise. Their office is located in the Barcelo Hotel. (I am pretty sure that's the dive op that Weiland is referring to in post# 4)
You can check them out at:
www.ixtapaaquaparadise.com
We were very happy with the dive op. They were very professional but also fun. Even though they were not our 1st choice, if we go back we will dive with them again. They have 2 six pack boats, so they can handle more divers than Carlos Scuba. He told us, on the phone, he only has 1 boat & can only take 6 divers.
Aqua Paradise boats leaves from Puerto Mio. It was an $8.00 cab ride from our hotel on Playa La Ropa, in Zih. One day we walked from the pier into Zih centro & took a bus back to our hotel.
I thought the diving was really good. We saw tons of rays, seahorses, lobsters, a large variety of fish. We did a night dive that was one of our best ever.
I'll post my trip report a later.