Again, the level of loss has nothing to do with CI success. The ACTUAL factors are age of intervention and age of implantation.
I agree, FJ. Docs say that Li (my 4YO) was profoundly, bilaterally deaf from birth, and she had no useful hearing and definitely no access to the 'speech banana' sounds during six months of hearing aid trials. Her first CI was activated at 21 months, her 2nd a year later. She's had no difficulty adapting to her CIs, speaks, hears, comprehends very well, and we expect she'll approach typical spoken language abilities for a child her age within the next year if we can ratchet up her vocabulary significantly.
That's not to say she "hears exactly like a hearing child," and we're very much aware that she is a profoundly deaf child with access to sound using her CIs.
We've not pursued AVT (although I think it's a very valid approach, as studies have borne out), although Li completed a year of weekly auditory rehabilitation (learning to listen with her processors) after the initial activation. I think that because she was under 2 years at implantation there was less "catch up," and she already had nearly 6 months of ASL, so developing a brand new language was old hat to her.
Key to her continued success will be the same factors that contribute to every child's success: literacy, vocabulary development, immersion in the language, etc. If our current bi-bi path doesn't continue in this same trajectory, if progress slows, we'll reconsider, but right now, we're seeing a very successful outcome despite no previous or partial hearing (and even with a later than ideal implantation) and without continued intensive or special AV training. The special efforts we're putting into her education are all focused on developing and maintaining ASL.