I've been playing in a very serious, very well ran online franchise for about 8 Madden seasons now. It's a ton of fun and is really the only way I choose to Madden anymore, really. It's a sim league with strict rules. No video game playing such as abuses glitches in the game, nano-blitzing, or anything else that doesn't normally happen in the NFL. It's fine if one like to play that way, they just won't be doing it in this franchise. For example, one will get bitched at if their RB's are catching 12+ passes in a game (G-Force, lol). VERY rarely is a RB a teams leader in receptions (if ever?) so it shouldn't be that way in this league.
Some of the players are just incredible. It blows my mind. They obviously have much more free time than I do.
Unfortunately, I don't get to play as the Packers. The guy that has them has had them from the beginning of the league. I play with the Steelers. It's not that big of a deal though because after the first 4 season the teams are totally different anyway.
I would highly recommend everyone getting into online franchises. VERY entertaining and strategic in a way that offline or ranked games can never be. The more popular they become the more features they will add, because they are lacking a bit right now.