In TTL mode it's very easy and intelligent.
Attach the flash and turn on; it should default to TTL mode. If it says FP as well that means high-speed sync (auto FP on Nikon) is active so if you or the camera choose a shutter speed faster than the camera's sync speed (usually 1/250th) it will still work but with a reduced power output due to how high-speed sync works. This is across all HSS-enabled flashes in all brands and not just this flash.
Flash compensation is easy in any camera mode; you can instantly press the crosshair on the rear of the flash to increase or decrease flash poet in whatever mode the flash is set to. You don't need to press a 'set/select' button like on many other flashes.
In any of the auto camera modes (P/A/S) it's been a very good flash in terms of exposure. Not all Nikons have a flash exposure compensation button on the camera but I find with the SB800 it's easy to just make adjustments on the flash using the +/- buttons anyway. I also like this because you're doing two totally different actions - with Canon it was easy to be altering exposure compensation instead of Flash compensation.
I use my flash a lot in full manual mode with the camera set to manual also but I have shot in (camera) manual mode with the flash on TTL and it's done a great job.
This is a very good link to understand flash EC -
http://neilvn.com/tangents/flash-photography-techniques/8-flash-exposure-comp/
What are you going to be shooting mainly? Might help knowing that, as there might be a few tricks you could learn
The SB800 is a really good flash and that fifth battery compartment is a Godsend for decreasing recycle times when you're shooting quickfire.
Remember that it has full override all the time so when it zooms with the lens you can just press the tree symbols (which control the zoom) to give the light spread you want. Same applies to output.