Alteration is pretty awesome, but I usually only go into it for the passive resistances. I never had a reason to delve into the other aspects of the school. The character I'm in the process of creating for the CB group though is using alteration for paralysis and telekinesis as well, and I've actually have found it rewarding. Just not high on my list of favorites personally
My favorites are Destruction and Alteration. I like combining the elemental cloak spells with the flesh spells, it's great for my warrior characters, and both of those effects carry over to the beast forms.
Alteration also provides useful resistance perks, as well as utility spells like paralysis and candlelight. Destruction has a good ranged magic attack, and close range magic for spellswords.
There's something to be said about each of the magic skills, but these two are just my favorites.