Played some matches online with funnyadit - first a 1 vs 1 match and then 2 vs AI co-op.
For the regular online, I think it was noticeably better than usual. I don't remember if I'd played against him pre-patch or not, but against how it usually goes to opponents in India, there was a lot less lag and a lot less weirdness. Obviously I'd have to play a lot more, and ideally against people I frequently played against before the patch (*cough*
@Biggs *cough*) - but my initial impression is a positive one.
Then played the first of two co-op matches, a T10 match batting first. About 5 overs in it crashed to desktop on both sides at the same time - so obviously no chance to save. The second one was completed just fine.
There's certainly a need to designate control of the hud to one side, aside from the obvious bug that you get the other team's info, there's things like when to take reviews and setting the field that seem to be able to be controlled by both players at the same time. I'd suggest for DRS, let one player make the final decision (so the bowler if appealing for LBW, the fielder if a catch, the striker when batting) but have the other player's choice show up with a symbol next to it to show what they think. For fielding, let the player currently fielding control the field set - ideally using their own local saved fieldsets, not just the host player's ones.
Running mixups were the main problem, again, a system to let users communicate through the button presses would be good. Perhaps one press of the run/cancel button makes the 'yes' or 'no' call verbally to the other player, with the second press, or both players choosing the same thing confirming it. Obviously this would be best played chatting on a headset while playing, so it's probably less of an issue for normal people.
The other thing is cameras - this should really be treated just like career mode when playing online. You can kinda simulate it by using the field lookaround button, but that snaps back once the ball is delivered. In local co-op (or local 2 player vs an online opponent(s)), both players should be able to individually choose their camera preference while batting/bowling.
Otherwise, aside from stability with the crash and minor issues previously mentioned (incorrect scoring mostly), co-op seems to be fairly well rounded.