I am doing a commercial installation, and need to go 30 feet with HDMI iincluding through a wall. This has to be totally reliable, so am willing to pay what it takes for reliable equipment. I've looked at longer HDMI cables, and HDMI over Cat5 extenders, and at least half the people have problems. This has to work the first time, without trial and error. Any suggestions?
Your context is wrong. If you go outside of a single souce-to-sink connection, HDMI was not designed for high reliability. It was designed for two things - 1) secure transmissions and 2) uncompressed video. In other words, if anything is wrong with the signal HDMI's correct response is no video and no audio. So, much of the "reliability" part that you've noticed is with the processing and not with the cable.
Having said that, for 1080p/60 you can run 30' of standard speed cable and you would be OK as long as it is high gauge cable. Same with 1080p/24 3D. If you want to go higher speeds (such as enabling Deep Color) then you'll need a High Speed cable. The Monoprice Redmeres are the simplest high speed cables over 25' since the use HDMI connectors. The cable actually doesn't amplify the signal but instead recovers it on the destination side. The recovery chip is "tuned" to the length of the cable. Cat 6 conversion is another good method but is (slightly) more complicated since you have to convert to cat 6 and then back to HDMI.
Really the best advice I can give you is to test thoroughly out-of-wall before installation. Use as many of the source and sink components as possible during the pre-installation testing.
Also there is an HDMI section of the AVSForum where we discuss HDMI limitations and best choices. It's about three sections down from this one in the forum list.