Well this definitely makes spells that allow SR MUCH weaker. They probably can't even hit most level appropriate monsters, but the big boon for weaker SR is that the SR armor properties which used to be useless are now incredibly useful. On the other hand, now Magic Vestment and Greater Magic Weapon are forever stuck at +2, meaning that warriors need to actually pay to get their +5 enhancement bonuses, which is a nasty nerf.
Actually, I just looked at the thread, you don't get the spell level as your caster level, you get the minimum caster level to get that level of spell as your caster level. This means it makes almost no real difference, except to blasters, and maybe a few other spells like Holy Word/Blasphemy that get ridiculous with high caster levels (though the people who use these spells typically have ways to boost caster level... so even if they only have a 15 base caster level, they'll find a way to boost it to 40 or so)