I have a vintage 1970 Moulton MK3 and a new TSR30. I lust after many more. I think I do because:

1) They are gorgeous. I love my old MK3 look. I love the space frame of the TSR. The designs are passion-inspiring. Kinda like Jaguar in the 60's and 70's. Or maybe Apple products, in more recent times.

2) Advanced engineering. Whether it's the Flexitor front suspension or the space frame or the offset rear triangle pivot (which reduces bounce when you pedal), you just know Moultons are well designed.

3) Well made. Individually hand made ( the current ones, anyhow.) Mine even comes with a "story" behind it. Seems a kid who worked at Moulton spec'd the bike out for his girlfriend in hopes of keeping her affection. He devotedly shepherded the bike through the production process. She rode it once, then dumped him anyway. EvilV bought it from the heart-broken kid. Then I flew to London to buy it from EvilV. This story is part of my bicycle. Don't get that with mass produced products.

4) Rarity. Very much so for the US, anyway. Adds to the cachet.

5) The ride. An earlier poster postulated that the Moulton's ride would be at least as good as the finest road bike. I beg to differ. In terms of comfort of the ride, the Moulton is way better. The wheelbase is much longer - 107mm vs 95mm. The suspension makes a world of difference on any terrain. The Moulton's geometry/design shines best on a fast, curvy downhill. Great stable, comfortable ride. The road bike is designed for fast acceleration and responsive steering. Comfort is secondary.

That's all that I can access from my lizard brain to explain why I'm irrationally exuberant about Moultons.