I watched Roger up close from behind the baseline at the USO in '06. He was supposed to play in Arthur Ashe but got moved to Armstrong because of delays. He was playing Spadea. I had spent all day that day watching tennis on the outer courts, just marveling at the level of play - I saw Gasquet, Robredo and a bunch of others and the consistency with which they hit absolute monster balls with accuracy was amazing. Gasquet was literally off his feet 2 ft in the air on every single shot. I even saw Nadal and Safin warm up for their match later that day. Nadal was chewing up this solid Asian kid who tried his mightiest to hit with power and Nadal was yo-yoing him like a rag doll.
So back to Roger. Here I was after watching all these top pros just blowing my mind. But Roger was different. Even the sound emanating from his racquet was unlike any other player. It was soft "thunk" compared to the harder sounds of others. He moves like a frikkin cat on the court. Now that you can tell even watching on TV.
What was most amazing to me watching him from behind the baseline was (and this perspective is completely different from watching on TV, where everything looks 'flattened' out) EVERY single groundstroke he hit looked like it was going to land out. He had all sorts of spin on the ball, side-spin, top spin, under spin and the occasional flat groundstroke.
Spadea valiantly tried to serve and volley, come into the net on Roger's second serves, but Roger was like warming up against him. He seemed as relaxed and sure as the player's I had seen practicing earlier in the day. BTW those serves are extremely hard to read. The times he served from my end, I watched with a hawk eye to see if I could tell where he would go and had 0% success predicting correctly. Again, it wasn't the hardest serve I had seen all day but perhaps the most relaxed and accurate.
So coming back to the original question here, I'm a 4.5 player who's been playing for a long time. I know many of you here are weekend warriors like me or worse. If Roger handles a pro like he's toying with them, and the pros can manhandle top college players, who would put any of us to shame, then Roger is many many orders of leagues above us. Don't fool yourself. Go watch the pros play.