The online play wasn't bad when it first launched. During the first month after release I played dozens of games and had lag in maybe 10% of them. When I got online access again back in December, I tried playing online Brawl again and couldn't play even 1 game due to lag (the entire match was nothing but lag and made it unplayable). Not sure how it managed to get worse in 8 months.
BTW, in the last vote I went with Animal Crossing: City Folk. Brawl is my favorite Wii game, but I refuse to play it online or support it in these votes until Nintendo fixes the lag (or at least return it to its March levels when you only had lag once in a while).