Its a tell definitely...but you still need to know the opponent and their playing style/s.
I personally use the Action Timer AND Time Out Timers to influence the actions of other players EVEN WHEN IM NOT GONNA PLAY THE HAND. Anything that you can do/used to to your advantage to mentally mess with an opponents train of thought is good.
(Note: Not 100% of the time, because it really IS incredibly annoying, but enough to raise some Blood Pressure for sure...a lot can happen in a persons mind within a few seconds...we are our own worst critics.
I say this all the time but the KEY, if you can call it a key, or Ol' Wives Tale...Old Wise Tell... "To win you need only to make fewer mistakes that your opponent" ...and a little luck from the card gods.
In real play... I watch for twitches of the
hands, finger tips, are they clammy/perspiring, lip biting/licking OR Cheek chewing, leg bounces, cards guarded or not...does the pattern change with their changing hand strengths...do they watch other players before looking at their own hands or focus- only on what they are dealt...do they take multiple glances as their cards pre-flop (They never change no matter how many times you have to look back at your own cards) ..do they have to look back post flop...everytime?...do they roleplay (create action when the table is dead) or do they still forget that they are the fn Big Blind again and you gotta keep telling them.
Is this a Shark mentality? If I see a Shark, I play dumb fish...I see a fish, I circle, chum, then strike as the shark...ALWAYS...not ALWAYS but SOMETIMES...SOMETIMES almost never...here and there...enough to hurt but not enough to create a pattern...keep it random...then Slap'em like Rick James...and tiptoe off... Im rambling...rumbling...mumbling...
Hope this counts as a "Quality" post/reply hehe