Played with someone about half the country (USA) away from me, lag was kinda bad in the first 2 stages, but then solved itself and for the last 3 the game ran swimmingly. Not totally unlagged, but it was fairly insignificant.
Lap 54 with Mami/Homura? Every single boss dies to... pretty much a single timestop/tiro finale. Even Walpurgis. Gertrud actually doesn't, simply because your levels are still low :V We were 90/87 at Walpurgis, by the way. Pick lap 65~70 and you'll start seeing double 99s at the end.
Also, did Lap 1101 with Mami/Kyouko for shits and giggles. You know how there's a giant anthony near the beginning? It took about 25 minutes to kill. I kid you the hell not. Spamming Tiro Finale and whatever kyouko's moves, it lasted between 20~25 fuggin minutes aihsdfklajdfsa
The normal anthonys took a minute or two themselves. I know it gets a lot less bad after you manage to level up, but it's ridiculous until you do. The highest lap you can clear is limited much more by patience then otherwise; with 3 people who know what to do, getting hit honestly isn't something to worry about happening. Unless you picked Kyouko/Sayaka I suppose, but with 2 people making sure to back them up with stunning or timestops, you could probably use them anyway.
By the way. You know the Grief Syndrome online thing? Gsonline? I keep thinking of it as "Gasoline". I mean really. It looks soooo similar.