To me, SC4 without online would have been meaningless, because during these pasted years I've been unable to travel & gather up to game with my nearest community players but only once. So online made-up for the miraculous 90$ I'd spend on SC4.
I'm consider myself a "core-player", not top-player, not average-player, etc. I began playing Arcades when MK1 was released, I went through lots of fun while learning the concept of competitive gaming until I got the hang of it during SC2 times. Yes, it took me that long, I was very young, but still I was already good enough to beat Battletoads on NES, heheh, try beating that game ;)
Anyway, playing SC4 online gave me lots time to experiment many things by playing lots of random good & new players. I could play & play without turns. During my offline days I wasn't able to participate & practice that much at tournaments because there where too many players playing for few consoles & because when the tournaments started I'd had the luck of having my 1st opponent being the winner of the tournament, which lead me to loser bracket right at the beginning of the every tournament I'd went, tough-luck huh?
My opinion about SC4 in general is that Namco made it slooooower on purpose to compensate for the lag they weren't able to handle with their netcode, & sooooo slow offline lol sooooo sloooooow wtf.
Playing online too long under the pressure of lag & spam have sharpen my reactions, it really did. But when playing offline after online, it hinders my timing on everything, but after some matches I get timing back.
Online is ok. But lag dose fuck-up many times...
anyway, I got bored typing..