I run a heavily home-brewed version of Swords & Wizardry. Many in my gaming group, as well as myself, enjoy the process of home-brewing, and even those who don't actively involve themselves enjoy at least some of the fruits of our home-brewing. As a result of over a year of home-brewing, we're starting to have a system that fits our group better than any game could when run "as-is," in much the same way that (I hear) tailored suits fit better than any store-bought, "as-is" suit ever does.
In fact, in much the same way that I think New School players are playing (rather than preparing for playing) when they work on their character builds, home-brewing, for at least some of us in the group, is an enjoyable activity in and of itself, not merely preparation for actual play sessions.
There is a downside to home-brewing, though it is, in my opinion, far outweighed by the benefits. This downside is decreased compatibility with just about everything else other people are doing. Probably the best example for my own game is the fact that, as far as I can tell, NOBODY except the publishers of Dungeonslayers and myself uses the metric system in Old School D&D. Distances are usually pretty easy to mess with: five foot squares are two meter squares and a mile is two kilometers- hardly exact, but good enough when exact conversions aren't needed at all. More fiddly is weight, especially since we use a kilogram-based encumbrance system. I generally can just say that two pounds is about a kilogram, but when goods are sold in lengths, weights and volumes, that requires conversion. I've received a refresher course in my middle school Home Ec classes just by having to figure out how to convert different Imperial volume measurements into liters.
The end result of all this non-compatibility that is most an inconvenience, though, is character sheets. With all the systems and rules we've bolted on- a small skill system, movement and encumbrance being done in metric, distinguishing race and class, and only slightly non-standard rules for hirelings and henchmen- plus the fact that no other game I know of uses a single save system like Swords and Wizardry does, it's little wonder that I've had to create a character sheet for us to use. It's nothing pretty, but it works and works well. On a lark, I'm posting a link to it here; it probably won't be terribly useful to anyone but it might be interesting, especially if you've wondered about the execution of some of the home-brewing I've discussed on this blog. Unfortunately, I can't figure out how to get my character sheet into a version I can post on this blog, but, thanks to Google Documents, you can find the PDF version here.