Argue ferociously about Sidereal Martial Arts in this thread.

Speaking seriously, I like punching spells into bits.  I mean, seriously- you see a dome of light separating you from something, or you're trapped in a demiplane sustained by glowing golden statues, or a conflagration shaped like a massive dragon is spiraling towards you, opening wide its jaws.  I find it oddly fitting that in this case, the straightforward answer is not 'Punch that sonovabitch', and that's precisely what a Sidereal does.  Very cool.

There are some minor problems.  First off, it is cheaper to punch it to bits than use actual countermagic.  Second, while it's awesome to have the wizened old man look at the cage of mirrors magically built out of nothingness and punch it to shreds, it's less awesome to have someone's ancient, epic curse blasted apart by a bored Sidereal (And cheaper than OAF, man!)

I generally adjudicate 'does this work' on a case-by-case, which is not really appropriate for the game because ST fiat is not how one should know when to use a charm, but... best I got, really.

But the biggest problem?  When you Spell-Shattering Palm someone else's Spell-Shattering Palm.  Do you know what happens then?

Nothing at all

Rim:

There are some minor problems.  First off, it is cheaper to punch it to bits than use actual countermagic.  Second, while it's awesome to have the wizened old man look at the cage of mirrors magically built out of nothingness and punch it to shreds, it's less awesome to have someone's ancient, epic curse blasted apart by a bored Sidereal (And cheaper than OAF, man!)

I would have no problem with SSP if it could only break spells as they are cast, or within the scene they were cast.  This would make Sorcery better at dealing with other Sorcery outside of combat, while SSP would be more martial-focused.

But giving the Sidereals an easy way to terminate longstanding Solar Circle spells when outside of combat basically makes it impossible to impose any longstanding changes on Creation with Sorcery, because the Sidereals (whose job it is to find a way to deal with such spells) will easily stop by and terminate them as soon as your back is turned.  This is a problem when making major changes to Creation is one of Solar Circle Sorcery's selling points.  (And there are severe trade-offs for this capability -- it costs a huge amount, is difficult to use, and so forth.)

I think it should be easier to do certain things than to undo them.  This is a basic part of the setting, since it ensures that the players' actions matter and adds weight to their decisions; it also makes it important that they deal with particularly dangerous opponents quickly, rather than let them do lots of damage that is hard to reverse.  If you Rain of Doom a city, the Sidereals can use Mending Warped Designs to repair it, sure, but it requires extensive work on their part.  Casting Enemy of Nature on a group should be a big deal, and what Spell-Shattering Palm says is that it isn't, really.  I would prefer it if Sidereals had to rely on Mending Warped Designs for dealing with such effects.

I second Rim and Aquillon's complaints with Spell-Shattering Palm. The basic conceit is great, the total implementation is... well, it breaks the setting a little.

I am basically okay with Spell-Shattering Palm.  Yes, it's cheap with a sutra, but the difficulty is usually high enough that you'd better put it in a Combo, which raises the cost notably.  It wouldn't break my heart to see the cost upped a bit anyway.

My biggest problem with SMA is player perception of them.  Everyone obsesses about getting them, and it seems like every time they're brought up, someone starts trying to think of ways around the "[insert splat name] cannot gain access to SMA" provisions (though to be fair, this has tapered off some since Dreams, and I expect will diminish even more with Glories).  SMA just aren't that useful, in my opinion, except for the styles that are broken.

And that leads me to my other problem with SMA: Almost all of the published styles are fucked up.  Some of the problems are small (Citrine Poxes of Contagion has form weapons, but every Charm has the Touch Keyword), and others are not so small (famous playtester Holden has gone on record as saying he has never been able to defeat a character using Obsidian Shards of Infinity Style).  So the players are striving for a golden trophy with a small crack that in its side that oozes poison.

before everyone keeps going. remember that sidereals can't make new native charms. SMA is all they have that lets them stand up to other celestial beings.

They have their pride