Some in my group have played around with them, and in general the riders are seldom worthwhile. Thundering Smite is the only one that saw any repeated use due to the Shove effect was sometimes worth the damage loss. Since it only cost 1 prepared spell, it was often kept for such situations. Everything else is pretty meh, except for Banishing Smite, which we didn't get high enough level to try out. Losing out on only 1d8 for a chance to blind seems worth it, assuming you can hold concentration.
IMO Divine Smite is what shouldn't have been in the game. Without it, the smite spells are right where they should be.
Man I just don't understand why folks are valuing ~1d8 damage so highly. From experience, frightened, blinded, even ongoing damage sometimes (though that one is too easy for the target to get out of early), are well worth doing 1d6 or 2d8 or 2d6 instead of 2d8 damage.
I mean, Branding Smite deals a meaningless shortage of damage, effectively the same damage, as Divine Smite, and the target sheds light and can't become invisible. IDK about you, but I face and use creatures that use invisibility often enough that it's worth it. I also can't imagine how a creature could ever become or stay hidden, while under the effect, since they're shedding bright light, I at least give them disadvantage if they try, as does every DM I know, and in a dark enviroment, a PC with darkvision might have advantage to hit them, since they're a beacon in the darkness.
My paladin has used Wrathful Smite with some success a few times, but it's pretty situational and it's rarely the best option. If you have preparation time, then Bless, Protection from Evil, or Shield of Faith are much better uses of your Concentration slot. If you don't, then it has its uses in debuffing enemies (like giants) too powerful in melee to go toe-to-toe with, and who have enough hit points that the difference between 1d6 (Wrathful Smite) and 2d8 (Divine Smite) isn't going to make a major immediate difference. Even so, Command ('flee' or 'hold') is usually a better option because you can use it at range, it doesn't eat your Concentration, and if it works, then it may provoke an attack of opportunity as your target flees, as well as actually stopping your target attacking rather than just giving them disadvantage when they attack you (the 'can't move closer to the source of fear' element of the frightened condition isn't much help when you have to be in melee to use Wrathful Smite in the first place!) Wrathful Smite's longer duration is a plus, but again, that's concentration-dependent, so it's not something you can rely on and it comes at a not-insignificant opportunity cost. If you're alone or have limited allies in support, however, Wrathful Smite can be great because unlike Command, you can actually attack as normal while it's active.
I've seen frightening enemies put to very effective use, over the years. You also have stuff like blinding smite, and the ranger's really good smite spells like hail of thorns and even ensnaring strike.
Is there any need to be stacking even more damage and even more incentive to nova onto the Paladin class?
In my games I like to restrict Smite to 1/turn, so these Smite spells get more mileage.
How would this do that? You'd, I guess, be able to run Divine Favor and also use the smite spells, as a paladin, but that's it. And hey, cool, that spell will get used sometimes!
Now, Rangers, on the other hand, would get some mileage out of this in terms of damage stacking, since they could run hunters mark and still use spells like hail of thorns and, eventually, lightning arrow.
I could see a vengeance paladin with magic initiate for booming blade running HM, hitting with wrathful smite on a booming blade attack, and then back up in a direction where the enemy can either stay put and do next to nothing or go after another character and get the BB damage while operating with disadvantage, but that's a pretty situational combo, and one that character can already do most of, anyway.
