But Heighten Spell is really good with the right spells.
Stuff like Glitterdust or Slow when heightened can easily compare with 5th or 6th level spells at the appropriate level. Also the enchantment school... Charm, Suggestion, Dominate. The DC is all that matters with those.
And it somewhat compensates the extremely low number of high level spells a Sorcerer has, since you can use the lower level spells as high level spells.
I've chosen Planar Binding as my first 6th level spell. Now I basically have no 6th level spell, when it comes to regular spellcasting. But I have Heighten Spell and Glitterdust, Suggestion, Dominate Person, etc. So I have very good and level appropriate uses for my 6th level slots.
Bye
Thanee