Iku Rex said:
I asked if you could have more than one change in effect at one time. He said "yes". I asked if you could make more than one change per casting of the spell. He said "no". It seems crystal clear to me. There is no contradiction.
It does not seem "crystal" clear to me, although your interpretation seems to be the most probable. One could also interpret "more than one change per casting" to mean growing wings, and then a few rounds later switching to gills, and then a few rounds later to claws, rinse, repeat.
Even if more than one change is not allowed in the sense that one can not keep changing throughout the duration of the spell, it still seems possible that one could have a single change that results in multiple effects for rules purposes. The example of a fish-man (or fish-gnome) having gills and webbed hands incorporates changes to two different body parts. However, a single change that adds claws could reasonably be used for attacks and for climbing. If balance is the issue, the gills and webbed hands do not seem significantly more powerful than the claws.
Note that I am not supporting either interpretation, I just want to get it right. But as I said before, for this specific character the DM's interpretation will be the right way, for his campaign.
For the record, I am still trying to think of other uses of the spell, to get the most out of it's versatility. So far, we have:
* Modes of movement, such as fly, swim, climb, burrow.
* Attacks, such as claw or bite.
* The ability to breath underwater with gills.
* Disguises (the +10 to disguise from the spell description).
* Possible circumstance bonuses to interaction-skills, such as intimidate, diplomacy, and gather info (by taking a form more likely to be accepted/feared by others).
One other thought to add, in case anyone is interested, I think I can solve the inability to hover problem by adding Featherfall when the character levels. If he really has to cast a metamagiced spell he just has to be sure he is up high enough that he will not hit the ground in one round, cast away, fall for a round, and then cast Featherfall. Or even plan ahead and cast Featherfall before failing to maintain flight speed.