Personally, i'd say no and yes.
Fun? Do you find making an ikea cupboard fun? Building a PC is similar. It's easy enough to do (just slot the pieces together), frustrating at times and you may need to take it to pieces and put it back together before it all works.
Practical, certainly. It's not hard at all. I'd agree with most that has been said, although personally i'm fairly disinterested in the parts - I'm not interested getting a tweaked, overclocked cutting-edge PC, just something solid and stable that does the job. That's probably because I work with computers, so I'm not interested in them as a hobby.
Definitely recommend it though. It will teach you something about how it all works.