Imperial society is undeniably hi-tech. Massive space vessels cross the void between stars, exotic energy weapons and shields exists, genetically engineered super-warriors stride into battle clad in futuristic power-armor, hive-cities are home to hundreds of millions if not billions, lifespans for the rich are measured in centuries, artificial gravity can be created and manipulated, contra-gravity fields allow infinite commercial transportation unto and of planetary bodies, and so on and so on. And the citizens of the Imperium take these things for granted (those living on civilized planets anyway), like we do aircraft, cars, TVs, and computers.

But there is one huge difference in how technology is perceived; it is part of civilization, but it is NOT understood by the general public. Indeed, there is a great deal of superstition connected to the use of technology, so when using a datapad you'd not only push the buttons, you'd also mutter some prayer to appease the Ghost in the Machine. If this is difficult to envision, think about this; what would it be like if you lived in a would where technology was very advanced, almost magical, only you also grew up in a place where there was no schools, and the only lectures given to you on technology came from your own father, steeped in the religious teachings of the Church, with a sprinkling of good old superstition added? You'd definitely not understand how it works, nor would you want to, since you'd be likely to consider technology a semi-evil necessity.

Another important thing to consider is that technology is not uniform throughout the Imperium, far from it. Whereas the rich and powerful have easy access to everything they can imagine (which is quite a lot), the poor are not so likely to be in direct contact with hi-tech devices. So on the same world you can find areas where archaic devices dominate, even if parts of the planetary population live in floating cities in the sky. Even in a hi-tech place like a Hive-City or on a Forge World there are those who live out their entire lives seeing technology and using it in a passive way, but never really utilizing it themselves. For example, a poor factorium worker might operate a few simple machines at work (with near-reverence for the machines, the spirits that live in them, and the Tech-Priests that attend them), might ride a hyper-velocity mag-lev train to and from his hab-block without ever thinking twice about the hi-tech hidden behind buckled panels and flaking paint, and might have a beat-up holo-vid in his cubicle which he spends most of his free time in front of.

The rich have access to much more technology and may also better know how to use it, but chances are they have servants and such to do any work associated with said devices. If anything the main difference in outlook will be that nobles recognize that technology is yet another power factor and is more willing to use it rather than fear it. Even the tech-priests, be they from Mars or local guilds, view technology with no small amount of reverence and superstition. They may know how it all works (some of it at least), but their knowledge is irrecoverably fused with faith and religious ritual.

Lastly, if there is anything the Imperium has enough of then it is a dirt-cheap and near-limitless pool of manpower. And with hi-tech considered mystical at best, or even outright evil, and the knowledge of its construction and repair understood only by the few, the Imperium has found another way of dealing with...just about everything. Just put enough men on the task and it will be done; if giant fusion-powered excavator-servitors are not available for the building of a new trans-continental highway, three million convicted criminals can do it in the same time using simpler tools.