I have one!
Things I like:
1. It's pretty rare - have a look on howmanyleft.com! I like that there aren't many around, in fact I've never seen another one
2. It's extremely versatile - depending on how you're feeling and what you need to do it's either a sports car, an estate (with the back seats down), or a long distance cruiser
3. It's comfortable and luxurious, albeit a bit of a hard ride over our pot-holed roads. Depends what you're used to
4. It's aged pretty well on the inside, it doesn't really feel dated. With the COMAND/nav and the panoramoc sunroof it looks and feels pretty modern
5. It's fast and handles well - I think I'd struggle to use much more power on a daily basis. There's not much it struggles to keep up with
6. It's understated and most people ignore it - nice if, like me, you don't want attention
7. Servicing and running costs are very reasonable
8. The 3.5 V6 sounds great
9. No supercharger or turbo to go wrong, just a nice big n/a engine, which may soon go the way of the dodo!
10. A lot of car for the money, especially if you find one with plenty of extras (panoramic sunroof, COMAND/nav, heated seats, evo sports pack, leather)
11. Long shot but...future classic...?
Things I don't like:
1. Highest tax band - annoying!
2. It does look weird from some angles, the back especially - I can never decide if I like it or not. However, I think the slightly odd looks add to its rarity and the fact most people ignore it. I like to think of it as 'interesting'! I do think it looks good from the front
3. BALANCE SHAFT! Google it if you're not already aware of it - a weak point in the m272 engine. An expensive repair if your engine is within a certain range (all 2006 ones are) but once done, it's a permanent fix. This does mean that the cars can be cheap to buy though. I'm treating it as a (possible) second installment

4. Visibility isn't great, the A pillars are thick, the rear side windows very small, and the rear visibility is poor. I got used to it after a while
I really like mine and am planning to keep it for a long time - I've had it about a year and a half so far.