Compared to the Classic, in my experience, audio-wise the Touch has better sound out of the headphone jack and better quality via digital output. The interface is nice, as one would expect, since you can use the touch screen and you can have album cover graphics. It's a little weird in that the font size automatically switches from small when you use the touchscreen to large when you use the remote, and vice versa, though for all I know there's a setting buried somewhere that I haven't found that can change that. I can see how that's nice if you have it set up in an entertainment center across the room, but isn't as useful to me since the unit is sitting right next to my bed. The screen, even on a lower setting, is also pretty bright so it is kind of like an unneeded night light for me. The responsiveness is also slower on the Touch than on the Classic, almost everything from startup to track seeking. I noticed this when I was A/B comparing the two since the remote activates both units.
All said and done, the Touch is nice and is an upgrade, but didn't blow my socks off compared to the Classic. The slight improvements in audio is pretty subjective and not massive, but I didn't feel like I wasted my money or anything. This is also mostly experience with the built-in DAC or with portable DAC/amps, so depending on equipment the effect may be more pronounced for all I know.
I haven't tried the built-in server yet. I'm planning on maybe trying that out sometime soon so I can use it as a transportable source for the next local meet. I have a spare USB HDD and a currently empty 16 GB thumbdrive, so it shouldn't be that hard...right? Famous last words, I know.