Attacking with Ray of Frost now creates a Frost surface and can instantly knock targets prone. If there is any blood in the area - and there almost always is if you're using melee attacks - it freezes a wide area of blood, which can also inadvertently cause creatures near the one targeted to also fall. Or worse yet, the targeted creature can make their Dex save and your ally can fail.
Acid Splash now inflicts -2 AC and creates puddles which also inflict -2 AC and also last forever. -2 AC is a +10% chance to be hit. Not being hit, but merely standing in an acid puddle inflicts a creature with the -2 AC, because apparently all attacks are targeting the bottom of your boots.
I am familiar with the effects: they just don't seem to be causing as much of a stir as flame effects are. I see your point about the Acid, though.
I really like the utility that surfaces offer. It feels very DnD to be able to cover the floor in grease before setting it on fire to burn a bunch of enemies, even if that isn't how those spells work in the rules as written. But getting the surface effect as a side effect of doing damage is a bit much. Making it a choice would go a long way to encouraging more tactical thought in how they are used.
I agree with this, and it's more fitting to Firebolt's rules text, which says that the spell can be used to ignite an unattended object if it's not directed at an enemy. It's base damage is 1d10, though (wildly)