Sorry, more questions about Aegis of the Hearth-
Not clear on the Aegis and persistent supernatural powers. Can a human without might but with Shapeshifter or Sex Change or something similar walk into an Aegis transformed, or will something unfortunate happen?
I think he can, but when in the aegis, he gets the level aegis like a malus on all his rolls for supernatural abilities.
If a magus MuCo'ed under a spell that does not have sufficient penetration to penetrate the aegis he is about to walk into, and he then enters the aegis, the spell is removed.
Naturally, aegis of the hearth is well known to function against supernatural creatures and supernatural abilities. If their transformation can penetrate the aegis, then it's fine. If it cannot, however, then they likely revert to their 'default' form. However, nothing stops him from transforming once within the aegis, if he can manage the feat.
I disagree.
The description of Aegis of the Hearth includes the example of a character with an Invisibility spell cast on him attempting to enter the Aegis. The RAW state that this spell is blocked by the Aegis (unless it has sufficient penetration). I don't see any reason why a MuCo effect would be any different?
I also disagree. The aegis functions like parma. It does not dispel magic, it keeps magic away from the protected entity. Te MuCo'd magus would be kept out of aegis.
Same thing for the invisible magus.
I stand corrected, then.
In that case, for the opening post, then the shapeshifter would have to revert to normal form if his supernatural roll does not provide sufficient penetration.
Your favorite companion and every grog in the Covenant have been turned into toads. They hop home, thru a large Aegis, and the penetration from the original spell is insufficient to penetrate - is it really "problem solved". 
So, that's why. Not just MuCo, but any such spell. The description says an Aegis "blocks" such spells, but the target doesn't automatically shed the spell at the door like a pair of muddy boots or a wet cloak - the Aegis stops them both until the spell has been removed by some other means.
(Which raises some interesting problems for both Characters who have had an unwanted/unknown spell placed on them (if they have no token), and SG's who wish to use such as a plot device. But that "blocking" itself can be a clue -if the local yokel driving the potato cart suddenly cannot enter, something's up!) 
See, I look at Aegis in a totally different way. You can't cast the spell INTO the aegis but once the spell is cast and the effect is there, it can pass. Your invisible wizard can enter the aegis and he is not physically stopped because the magic is on him. The spell transformed wizard walks acrosst the aegis and he can enter.
Now, if the grog was inside the aegis and the caster outside the aegis then it would stop the casting in the first place but once the grog is a rabbit, he can hop home to try to get help to save him.
the alternative is that the magic is stopped by the aegis so the invisible wizard enters but invisibility ends. Grog becomes rabbit, hops home and is normal inside the covenant but the moment he steps out, he is suddenly a frog again.
I am not sure though that shape shifter or lycanthropy is necessarily the same as a Spell though.
So, once cast, it's just there? That does solve several problems. One limitation would be that the spell cannot be "interactive" - something that sends information somehow - then that would have to win over the Aegis.
So, in that houserule, an magically invisible or transformed creature would not change back or be "blocked", but nor would a character with a large "healing" spell find themselves either unable to enter, or their wounds suddenly re-open upon entering.
Good question. It looks like that the shapeshifting and lycanthopy granted by the virtues do not need to penetrate. Rulewise, they do not have an effect level, they do not require a die roll (or to match an ease factor, but ot an effect level) or spending of might points. I would put those in the same category like the capacities of the nightwalkers or the heartbeast. The nightwalkers are not held at bay by the Aegis (Hedge Magic p118). Why not say then that none of the above are hindered by the Aegis ?
On the other I differ with Ladyphoenix as my take is that is that spell are blocked (and their target too, in a way similar to the effect of parma magica), not dispelled, but blocked. It provides opportunities for stories, some were mentionned above.
Xa
Personal spells don't need to penetrate MR, I believe.
So if the Aegis is a sort of huge Parma Magica, it shouldn't block personal spells. It does block 'personal' invisibility, since that spell affects the species, not the person.
Just a thought to stir the debate.
The Aegis not a "huge Parma magica" - the rules are not identical for each.
Cuchulainshound - what is a potato cart?
Err - that last comment should have been followed by one of these 
In this case, I think it's like a dikfer. 