I've used healing hymn and it sure works fine. Doesn't work with cure minor RAW, but you should ask your DM, especially if you're the only one doing the healing.
I saw that you revisited your opinion on Healing Hymn and colored it blue, but I was curious if you were taking into account the
Complete Champion errata which limits the bonus healing to the caster level on the spell.
Ex.) A 3rd level Cleric casting
Cure Light Wounds would normally heal 1d8 + 3, with a maximum of 1d8 + 5
Under the effect of a Healing Hymn (with 6 ranks in Perform), it would not be 1d8 + 9, but only 1d8 + 5 since the
Cure Light Wounds spell has a maximum of +5.
I can see it being effective if you cast the
Mass versions of the
Cure spells, since those spells have maximums of +25 to +40.
The errata seems to hurt this otherwise very useful ability.
(BTW, your avatar is waaaaaaay too distracting!
I <3 RLC)