I think the bonus invisibility XP with SeeI is already removed.
I would agree on the 'no Slow Monster on yourself' as well. I've sayt and thought about it, and other than XP, I honestly can't think of a reason to cast it on yourself.
As for the 'XP bonus', I would say leaivng it in place is useful still. Without the spell, there are fewer ways of abusing it, and what ways there are are a lot more risky, I think. Enough that it wuold make it worth the XP. Sure it's still scummable, but less so and with more risk, I think.