My friend played Melee for as long as I knew him on an HDTV, he played Falco and was better than me a lot of the time (we mostly did Falco dittos). When I went to his house the lag was there but not horrible (I've been to three other friends houses with horrible lag HDTVs, his had the least) so eventually I got use to it to a certain degree, and then each time I went over I would have a certain starting point of getting re-use to it again until we played an hour and I reached my maximum I could get on it.
When he went to my house and played on my CRT though he said he could slightly feel the difference, said it felt good but he wasn't amazed or anything by it. He seemed to be able to play the same, though I think he had a tad of adjustment to do, but it seemed like 2/3 or less of what I was feeling with his TV in terms of adjustment degree.
I started playing P:M wifi v1 and v2 during some of the later times I went to his house, it kind of made me better at the lag but it's still very different than the lag on wifi: the lag on wifi I could adjust to easier.
The only thing in terms of reaction was that I could get up-throw rest on his Falco with Puff and he usually wouldn't DI to escape it in time, either I was better at it than he was or the lag made it worse. I can't really remember all the details.
So are Laggy Tvs and Wifi detrimental? Probably. Are you enjoying the game more because the screen is so big (use component cables noobs) or because Wifi makes it so convenient to play people all the time? Then it's more beneficial if it's getting you to play. Playing Wifi doesn't have any kind of "oh no it ruined all of my skill" thing, your technical skill stays really in tact when you go offline (hell I might even say it makes you slightly more technical when you go offline sometimes). What is changed though, like other people's posts describe, isn't your tech skill but your tactics. If you start learning the game through Wifi first before offline, it's similar in a way to learning Brawl and then switching to Melee, obvious tactics you might know are wifi only but there's a lot of subtle stuff that you might not catch. There IS a difference between Wifi and HDTV lag though, in Wifi you can sometimes DI better due to the game actually being slowed down, while on HDTVs you might just lose a bunch of opportunities to DI. I still think that there MIGHT be some things that DO get more "able to predict" or whatever like the silly guy on the Wiki wrote, but if anything I think you get that more from Wifi since it's slowed down as well as laggy so it's like your in training mode on half speed, but I'm not sure what to say about the HDTV's lag aspect.
