Based off my initial findings, it appears that non-firearm related homicides are somewhat higher in countries that have blanket bans on guns. Example: there are as many stabbings per capita in Finland as there are in America. That's pretty counter-intuitive based on Finland's far lower crime rate and standard of living. Congratulations to all of the really, really funny people who contributed to this thread. You have managed to indirectly convince me that gun control is possibly less effective than advertised.
Does gun control reduce gun-related violence? Yes. It's undeniable. I hope that at the very least those who are in favor of our lax policy at least admit to that.
On a more serious note, gun laws are a reflection of the social norms of their community. Blanket gun bans succeeded in England due to a lack of any substantial gun culture there. They could make it legal to buy an AK-47 at your local pharmacy and I suspect few people would. On the other hand, gun control laws are lax in the United States due to resistance from a deeply ingrained gun culture. If all guns were banned here, many people would just buy them illegally.
My point is, there are plenty of reasons to think that gun control doesn't work that well. I am sure that it is not completely ineffectual, but its proponents are best characterized as hyperbolic. Well, that's true for any side of any issue. This is politics, after all.