*If you don't wanna read all this, basically I'd take the fun and learning of DIY any day over commercial products that I don't understand personally, unless it's an excessive hassle, which is rare for me.*
I have yet to build my first amp...but I'm HELLA excited for it. For me, DIY things are all about the fun, learning experience, gaining new and exciting skills, and hopefully saving money.
I'm a big hobbyist, mostly expensive hobbies. The DIY hobbies of mine are by-far the most FUN! I just really love making something and knowing it's my work, and that I can take full credit for it. I also know exactly how it works, and can tweak it, improve it, and play with it knowing it's my little creation. Having loads of new knowledge that the average person has no idea about is also a ton of fun. Even if someone has made something similar, it doesn't matter. I made it, it took my work, and I had a ton of fun along the way!
In case anyone is interested, the hobby of mine I'm talking about is computer making. I've built only 1 of my own computers so far, but it a great experience, and I'm still enjoying my computer since 2004. There's nothing like knowing I made it, and it rocks. I also love knowing that even if I break it (which I have, and sometimes very badly) I can ALWAYS fix it. Always. I can't even imagine having as much satisfaction if I would have bought a high-end Dell in 2004 to compete with it.
Another great thing is being respected by and being able to respect other computer builders/DIYers who also share the extensive knowledge that I have.
LEARNING, FUN, AND PASSION IS WHERE IT'S AT!