With all the new classes added there are some pretty neat combinations, sadly one combination I have found with prestige classes is going 20 caster and then spending the last ten available levels on prestige classes. Over all it has some neat possibilities, but one issue I have found concerns epic spells.
Epic spells such as Dragon Knight, Greater Ruin, Hellball, and Mummy Dust have a somewhat awkward requirement criteria.

As written you only need to be of 21st level and possess 17-18 levels of any class capable of casting ninth level spells, the issue arises here:

At level 21 of one of these classes you gain a feat called 'epic x', x being your class, this is the actual requirement to be able to cast these epic spells.
My suggestion is to adjust this to the as written requirement, allowing epic spells to be taken by any character of 21st level possessing the ability to cast 9th level spells, or at least restricting it to 20th level.
Thank you!