Back when WoW launched I was still on dialup, and played far too much for my own good. Part of playing on dialup was getting used to the latency, like 'queuing' my follow-up spell casts when my current one was anywhere from a fraction of a second to 0.5s from completion, so the command would arrive at the server just as my current one finished. As a healer this was important to avoid dead time where I could be keeping the tank alive.

It wasn't until into the 2nd expansion that I got broadband, and hoo boy was it hard to adjust to. Suddenly I didn't have to anticipate and plan ahead nearly as much, and I had a whole new learning curve to go through to get my timing on point again. It seemed to me at the time that the game was structured pretty decently to handle the huge differences in player system specs and connection capabilities.