Hey people... Thanks for replying. The guy who confused me a bit, also clarified it for me too. And I think it's very usefull for others to read too. It's a lot of text, so if you're up for it. Enjoy. 
Just to make it clear. I did NOT write this text, it's Voop's... I hope he doesn't mind I'm posting it. I just really find it worth reading. Enjoy!
oxtox is a bad thing. However there are not really any absolutes as to when it becomes toxic. As a matter of fact, there are two different toxicities, which can incur: pulmonary tox, which is due to long term exposures. That rarely happen in diving since it requires 6-12h or exposure to high PPO2. The other tox is CNS toxicity (central nervous system). This CNS-tox incurs as a function of O2PP exposure and time. I.e. it may be "safe" to breath O2 at a PP=1.4 for x min, but if you breath O2 at a PP=1.4 for x+x min, you may get O2tox.
So as you can see, it's not a hard and fast rule that PPO2>1.6 -> "danger". It is more of a pragmatic observation that "staying below a PPO2 1.6, and the risk of O2tox is sufficiently low to be acceptable.
A diver can be very "tolerant" against O2tox on one day, while on another day be very suceptible to an O2tox "hit". It's different if you're "staying still" or if you are exerting yourself. It's different if you breath in a wet or dru environment: you risk a "hit" at lower PPO2 in water than in a chamber. A "hit" under water can be fatal: convulsions. While these are not dangerous, and disappear after a while, they do cause spasms,contractions etc in the face - often causing the epiglottis to close and cause you to spit out your reg. When you recover from the convulsions (a minute or so), the reflex is to breath -- and without the reg, you'll get water -> drowning. If your buddy tries to make you ascent when convulsing, then you may do so with your epiglottis closed -- which implies pulmonary barotrauma. Remember: never hold your breath. Thus, if your buddy is convulsing, you should (i) maintain him at current depth (ii) hold your octopus against his mouth while pressing the purge button. That way his first breath after convulsions will be air, not water.
O2 tox is, like dec theory, not entirely understood yet. We have models which work "mostly". For deco theory, that is the gas-diffusion model and for O2 tox, it is the "CNS clock". Used conservatively, and one is safe. However they are models, and have no direct correspondance with the human physiology. Occationally, someone discovers more complete models.
A group of divers, such as those from WKPP, routinely do dives which according to the "traditional" models are not safe. It's not because these divers are "supermen", but because they've discovered a different model which, in their situations, better model their physiology and so on. Still, what they do are also just develop new models and test them. Noone really knows the complete details of CNS tox and deco yet.
So to answer your question: what happens if you go to 1.7 bar PPO2? Well, what happens is that you bring yourself closer to the area where a risk of a CNS O2 tox hit is likely. You may convulse -- or you may not. I've done up to 4 bar PPO2 without any problems -- in a chamber (where potential convulsions are uncomfortable, but not fatal). The chamber operator told me, that this was fairly standard for hyperbaric therapy. I would not cross the 1.4bar PPO2 limit in the working part of my diving. Currently, I switch to 100%O2 at the end of my 9m deco stop, when I am about to head up to my deco stop at 6m. This is, to me, reasonable since I am on the way up, and am not exerting myself: remember, there's air in the lungs, and the first few breaths of O2 will be dilluted by that -- and I will be arriving at 6m (1.6 bar) after just a few breaths. I do not reccomend that procedure to anyone, but it is what I do when I dive for myself.
(again... this is info comes from Voop, not me) :54:
