The flight model is really a sim. As a sim, it is as complex as a sim can be. There are some automated assist things to try and help out with the flight controls (i.e. brings "space flight" to more like "atmospheric flight"), but for those that really want to take advantage of what a true space flight physics allows, you can typically do so if you understand the controls (and have actual controls yourself to be able to do so).
Think of it like Microsoft Flight Sim, or Digital Combat Simulator World level of complexity. It is a true skill based system that will take some time to learn the skills (but for people who have some basic skills from other flight sims, or real life experience, a lot of that can apply and help cut the learning curve).
The walking around is just like pretty much any other FPS, so you should already be pretty well familiar with it and can adapt to the specifics of the gameplay in this game's universe. But the flight part will take some practice. I am absolutely not that is good by any means with the flight, but I still find it fun.
If you really want to get good and take full advantage, I highly suggest dual sticks, mouse, and flight pedals for controls. Yes, most people can get by with an Xbox controller, but it won't let you take full advantage of the 6 degrees of freedom for control surfaces that you need for a space flight sim. You essentially have the same controlability as a helicopter does (and a little more, but you can effectively fly in one direction, while pointed in a completely different one, and you may want to be able to still control the direction of your thrust, pitch, roll at any point in time to pull off the most complex of manuveours).
Personally I wish there were better flight sticks that are designed for space flight sim at this point. What you really need is something that has an analog thumbstick (like on an Xbox/PS controller) on a flightstick with z-axis twist capability, as well as foot pedals and a mouse. This way you can control all 6 degrees of motion with the single stick and pedals and still have your hand on the mouse for controlling gimballed/turreted weapons (and quick change over from flight to FPS controls since you just need to move the one hand from the flight stick to the keyboard). You will also probably want some kind of voice control as well, using something like VoiceAttack to setup macros and perform things that would otherwise be multiple keyboard inputs (as well as inputs that you might not remember the keyboard controls to perform, but you know what you want to do so you can basically say something like "balance shields", "all power to thrusters", or "stealth mode", etc...