Played a few rounds of grind yesterday. Can't say I like it nor dislike it, this will be exactly like metro/locker for me : a few games here and there just to put my brain in OFF position. But the overall feeling is a bit different from Metro, yes you still have the crazyness of kill kill kill moments, but Metro could be really great when you have a team pushing coordinately and achieving a breakthrough to cap B after being hammered by defense. No such thing in grind (at least for the few matches I played) as there's no clearly established chokepoints and players can easily flank to cap A or C (except may be in Devastation if you want to take A). But even if you can flank, the first team to B will be the winning one. On the 8 (very short) matches I played, we won all of them by a huge margin as we were always a bunch of players running straight to B.
Re. the maps, Devastation is...Devastation, that's the closest one to it's normal CQ variant, nothing really special except if you want to push to A and the opposite team is just camping (but if you want A it means that you already have B and C so at this point the match isn't really moving anymore) .
Rotterdam is borring, all the action is almost exclusively on the tracks, not the ground, you can't see shit for almost 75% of the match as soon as medics start their smoke barrage because of the extremely narrow playground + the train wrecks blocking aim sight (I think i made half of my kills without seeing the target just firing through smoke...).
Narvik is OK, can be fun with many covers giving you the opportunity to move forward on the 2 levels with possible flanking on the ground level.
Twisted steel is... so awfull that it made me laugh really hard, this is medic and support heaven, if you need any "X revive/heal/give ammo/use grenade..." for your assignments this is where you need to go, it's completely crazy with both teams facing each other 10m away. I think I spend 45s not moving just throwing continuously ammo to my teammates, same with med packs and I'm pretty sure that if you need the "X revive in one life" this can be achieved extremely easily in this mode/map. The lower corridors made for flanking just don't work : 1 or 2 snipers can hold it too easily and it's clearly the best way to die almost instantly this makes flanking by this route almost impossible, I played twice on TS and each time 95% of the action was on the bridge, and anyway I didn't have the feeling that anyone was looking to try to flank but clearly going for the full front assault. MMG are king obviously, but medic can also have a lot of fun.
I'm pretty sure this mode is here to stay and will be one of the most played. This kind of meat grinder mode exists in BF since a long time and even if it will never be my prefered one, I think it's a key for player retention which in the end will benefit the whole community.