A bit of a labored process, but here is how I watch Guitar Tricks videos on my iPhone:

1) Download the flash video file from the site (use the download option in the video viewing screen on the particular Guitar Tricks lesson page)

2) Convert the .FLV (Flash) file that you have just loaded to .MP4 format using a video converter software package - I use Free Studio by DVDVideoSoft as it is free! :-)

3) Copy the .MP4 movie file to your iPhone via the iTunes application

4) Play the lesson on your iPhone