Hi,
I've been using knowledgenet for a while, but not for CCIE but for CCNP, CVOICE & CIPT.
At this level, i can tell you that they are state-of-the-art learning tools, i'm using the express product they have.
They includes hands on labs that are really neat but if you expect exam crams, real questions or enything else like this, this product is not for you, because what they do is to teach you teh concept and techology behind everything that is covered in the respective cisco course but is not question cram oriented..
Other site with very good instructors and very high quality is cbtnuggets.com, but once again, i don't have a clue about CCIE....
They both are pricey, but once again, quality allways costs more, which is a shame because sometimes its very difficult to get the means to buy them.
Hope this help....
Pepe