My personal experience with homebuilts has been limited to 3 different designs - one of which suffered a structural failure while I was flying it. It had a factory built "experimental" composite propellor and threw a blade, the resulting vibration broke the engine mounts. Luckily, the engine failed and shut down before falling from the airplane or I would have died. As it was, I had to make a forced landing in a cornfield. The airplane had amphibious floats which tangled up in the float braces and when everything was finished moving I was upside-down in a ball of metal and fabric. LUCKILY, I was able to walk a way from it.
Personally, I avoid homebuilts like the plague, although I have to admit that some, like the Lancair can be pretty compelling. (I get to Redmond, OR, where their factory is several times a month and I've been through the factory many times.) My main problem with homebuilts is one of quality control. Unfortuately, the old saying "Beauty is only skin deep" can be applied to many builder's aircraft.
Granted, if you take a proven design and a skilled builder, you will end up with something that is far superior to anything that you can buy out of Wichita. However, there are MANY caveats that you must be aware of...
1. The insurance market on certain high performance models has gotten very resticted recently and some of the companies have pulled out of the market entirely.
2. Builder's liability issues still remain. It was builder's liability issues that all but killed the US light aircraft industry for about 10 years. It took an act of congress to pass laws which limited a manufacturer's liability to a finite period. If you built a homebuilt you are the manufacturer and you have a certain liability if you sell the airplane to another party. Most people find it "legally" safer to turn the airplane into a non-flying static display after they've decide to stop flying it. You see a lot of them donated to museums for the tax write off.
If you want to build one for the pleasure of building one, go for it. A lot of people will find that the investment of time and money are hard to justify. It's been said that if you spend the same amount of time working a second job or working overtime as you would spend building you're dream plane you could buy a good used factory plane. (Me, I would never fly anything I built.