I just hooked up a pair of Analysis Plus Oval 12 Speaker Cables. Although I've heard a lot of systems over the years I never tried messing with cables. Most of the audio people I know are musicians and recording engineers and don't believe in the cable thing. I really wasn't looking for new cables, but since discovering this site, I thought I'd give it a try. I chose Analysis Plus because their approach seems to be based a lot on actual measurements.
After listening, my basic conclusion is they made a difference but don't use cables to dig a rig out of a hole. It's a nice way to squeeze a little more out of one's system. (I compared the new cables to my old pair of Canare 4s11). The biggest difference was how much cleaner the bass became. It seemed like the cables just took away some gook, and left a cleaner mix underneath.
Visually the cables are well made, look nice and are flexible and easy to install.
Actually, before the cables arrived, I tried a pair of Oval 1 interconnects. They also seemed to "clean up" the sound a little. Even though it was easy for me to A/B because my cd/dvd player has two outputs - I could switch on the fly - the difference was very subtle. (My other interconnects were also Canare).
I would recommend the Oval 12 and the Oval 1, as a combo or on their own.