All matchups:
• Queens will sit further behind your army when defending attacks, in a safer area. It will be noticeably easier to keep them alive.
• 1 queen will be able to kill a scouting worker than runs right by the queen now! (if the scout tries to skirt around the queen it should survive, provided it's not at a choke) Also of course it will be harder to fully scout for what buildings zerg's made.
• (probably not worth reading

The unique situations where you built many queens to defend vs air, and you didn't take much damage, and then decide to counterattack because they're vulnerable (often they are depending on their air units to keep them temporarily alive, which is where your queens come in). Well now if you attack with army + queens, queens will probably hit ground stuff now too.
ZvT:
• Queens will be quite a bit better at pushing back a hellion 'contain' (so you can safely spread tumors)
• Will help defend bunker rushes (attacking scvs building bunkers, marines).
• Hellions (range 5), marines (5), and reapers (4.5), will no longer kite queens without taking hits. They will just generally be better at dealing with most terran units as they are no longer outranged by most of them.
ZvP:
• Stalkers (range 6) harassing queens will be slightly easier on the zerg
• Defending zealot harass slightly better
• Very situationally help vs cannon rushes (particularly the 3 pylon wall below ramp can be safely hit now by a queen. It takes exactly 1 ingame minute for a queen to kill 1 pylon.)
• Just generally be a little more useful at fending off early rushes or small attacks.
ZvZ:
• When you've 2 queens blocking ramp while lings attack your spine/s, now your queen can often attack back while standing there.
• Better at denying baneling run-bys
• A bit better at dealing with ling harassment
• Hatch-first builds in particular will be slightly easier to do/better than it is now.
• Situationally vs roaches (queens will outrange them), like when they're on hold position behind your mineral line when they went around your spines.
• Some zvz timings involve roaches/queens/infestors (usually vs muta builds) so they may be marginally more useful there (though they're mostly for antiair and transfuse still).