I can only pass on my experiences. Bought mine almost exactly 1 year ago with 21K on the clock and have covered over 6,000 miles since then including a trip down to Umbria (Italy) and back. I have suffered few problems and I think that most are acceptable for a 12 year old hand built car: -

1) Stearing lock jammed (now replaced)
2) Fuel Line perished and split under the armoured casing (There was a smell of petrol for some time but could not trace a leak until it really gave way. Very dodgy)
3) Usual oil leaks (fixed for the time being)
4) Aircon didn't work (Recharged it with a DIY pack from Halfords and still working fine 9 months later)
5) Dinged one of the catalytic converters in a Car park in Aix en Provence (Now needs replacing)

The lack of posts in the Mantara section suggests reasonable mechanical reliability my real concern is the risk of Chassis rust on a Mantara that is in daily or regular use. Perhaps longer term owners can provide more relevant comment.

I have not regretted one minute of the last 12 months of ownership.

I hope that this helps.

Good hunting