I ride a custom build on a Masi Gran Corsa Premio (2006) frame. I love it. It's light, stiff, and flashy. It was a great price too. The bike definitely turns a lot of heads because everyone around here rides Specialized or Trek.
It doesn't matter to me that the frames are manufactured in Taiwan. Why the hell should I care as long as it fits right and rides right (which it does)
I've gotta say that I'm less than impressed with their service though. I badgered them for weeks to send me touch up paint so I could repair a slight scratch (I'm OCD about that stuff) and ended up giving up because they stopped responding to my emails.
If you can get a good deal on a Masi frame, I say go for it. They are very nice.