I have been trying this practice from time to time without much success.. Watching shows without the sound or subtitles on. It just gets way too hard once past some point beyond catching up on the conversation where I give in to subtitles for me to see what they're saying.
Obviously I need to persist to see better results...
I've noticed it is pretty hard for me to catch speakers with an accent.. a southerner for example. An example from one show (Reno 911) - it's fairly difficult to understand a female who portrays a southern accent, but it's easy to understand the african american female who somewhat seems to drag her words out and slower. I don't know why it's this way, but I assume it may be due to how my experiences are growing up.
Lipreading some languages must be an impossible feat. I have experience with japanese, chinese, spanish and korean. Due to the similarities in the basic "alphabets" and differences in tones some of in these languages, it makes it quite a feat.
For example, the Japanese incorporate the a-e-i-o-u alphabetized system which would be a challenge to grasp.
The koreans drag and aggregate their words. "sekkisei kose-jjang"
In chinese "da" can be pronounced in 4 tones - da, da1, da2, da3, da4. Similar examples can be seen in japanese.
Now if any of these non-native english speakers then attempt english, it is hard to follow their lip patterns.