Eric Raymond has written some about guns and his fondness for shooting.
Some of the enjoyment people get is perhaps because they're engaged in a task which is complicated enough to keep their attention, but not so hard it's frustrating - as described in Flow by Csikszentmihalyi.
I think there's more to this than that, though - you can get some satisfaction or fulfillment from any number of tasks. I find that I get the most satisfaction from doing things which not only create a "flow" experience, but from those which enhance or maintain my own self-sufficiency and proficiency at important things.
Computer/net-related things are on that list for me - as is shooting, though I haven't taken up reloading, and law, and electronics, and auto mechanics, photography, and politics. I really enjoy learning about, manipulating, building, fixing, and teaching others about the things that are important to me in my environment. (The list above isn't complete - there's tons of other stuff I want to learn about - but real learning takes time, and resources.)
Also, I enjoy working with things which are susceptible to tinkering and hacking and exploring - like Unix, like older cars, like 1911-pattern semiautos or AR-15's, like PC architecture hardware. I can appreciate the quality and design of some things which aren't really intended for tinkerers - like Macs, or Glocks, or newer BMW's - but I find I don't enjoy using them as much as I enjoy using things I can monkey with myself. (That's not meant as a slam against those things - there's a Glock in the gun safe on my nightstand, and I bought my mom an iMac, just because they're hard to screw up if you're not in a good position to fuss around with details or appreciate configurability.
Some things - like modern 35mm SLR cameras - can give you the best of both worlds. I've got one of those fancy cameras another commentator didn't like. I bought it after spending a day with another friend who took a lot of unrepeatable pictures with her manual 35mm camera - turned out after we developed them that they were underexposed due to misconfiguration. It's great to have the ability to monkey with aperture and exposure when I want to take artistic risks - but it's also really nice to be able to use the "green box" setting (on the Canon EOS series) and be confident that I'll get sensible exposures if it's crucial that I get a reasonable if less expressive exposure (like these from a protest in Berkeley - no way I'd ever get to reshoot, if I'd judged the settings wrong.)
I think there's a lot of crossover between different vocations or hobbies that are susceptible to people teaching themselves about technology - some people enjoy learning, and enjoy a feeling of understanding and mastery over their immediate surroundings. I realize that sounds kinda old-fashioned and macho, and not very PC - but it's what I experience. It feels good to know that I built my computer from parts by hand, that I set up the OS myself, that I keep it running myself - that if my truck breaks I can fix it again, probably with the tools that I've got on hand, that my home is comfortable for me because I've made it that way, and I can protect myself and my dogs and my family from harm which others might cause.
Am I in control of everything? Nope. If the hard disk crashes, I don't have the skills or the tools to recover it at the hard disk level. I've rebuilt engines, but don't really have the time for that any more. If an earthquake swallows my home, it's gone. And, sure, there's a limit to the protection I can expect from my own weapons and training. None of these things is absolute.
Still, I feel a lot better when I'm operating in a world where I can understand what's going on, and how to change it if I want to. That's the underlying motivation behind my adoption and use of open-source software, and a lot of other things, too.