Hrm. I'm not convinced immuno-suppressants would be required. People inserting metal into their flesh has been happening for millennia (I personally have my ear pierced, and had no adverse effects), non-invasive neuron triggering is possible already (whilst the caps required for those are quite unwieldy at the moment, that tech can only improve), and it's not exactly like current prosthetics, which are, of course, just primitive augmentations, require immuno-suppressant drugs as far as I'm aware. Nor, indeed, do pacemakers or artificial cochleas - which, again, are primitive augmentations - to my knowledge.
Therefore, it stands to reason that advanced augmentations such as strength-enhancing limbs or replacement, more efficient organs, should not require constant immuno-suppressing drug usage, which does, regrettably, still leave the potential for external control. The only possibility there would be to ensure that all prosthetics are deaf and dumb when it comes to signals from outside the body, but that would be disadvantageous if it comes to brain augs that could be used to bypass computers and get straight onto the web...
Anywhom, I'm big on human augmentations

I would certainly upgrade myself, given the chance: I personally don't plan on living and dying on this one little rock, I'd like to eventually upload into a fully electronic chassis and live for centuries exploring the universe, or simply the cultures that we humans create in them. We've been augmenting ourselves since we developed the sharp rock that makes the spear, and now we get the chance to bring those augmentations inside the body. It's not exactly like our previous inventions have had no impact on our internal workings; the internet, whilst being a continuously external influence, is demonstrating just how plastic the human brain is, so we're just taking the next step.
In regards to losing our humanity, I always point people to Aaron Diaz's A Thinking Ape's Critique of Trans-Simianism, found here: http://dresdencodak.com/2009/05/15/a-thinking-apes-critique-of-trans-simianism-repost/