Is orbital hybridisation real?
Orbital hybridisation is, like most other topics bordering quantum mechanics, just a model of reality (in fact, I would go as far as to say like all topics ever thought of, but lets not get too philosophical). As such, there are limits to its usefulness, so models should never be thought of as a "true picture" of anything.

Models are always simplified and in the end "wrong", but sometimes they are useful. Through models we can gain insight and make new predictions that can be falsified or not and as such we advance our understanding (and the most learned even advance science as a whole). Without models I would not understand anything, but I considert it counter productive for myself to think of them as representing some "truth". 

$$\text{Observation} \rightarrow \text{interpolation} / \text{modelling} \rightarrow \text{prediction} \rightarrow \text{experiment} \rightarrow \text{observation}$$