Almost bought one of these so did quite a bit of research at the time
What year are you looking at? Looking at the picture it looks like a MK1 which IMO is the one to go for, mostly due to the lack of the DPF, if you do a lot of short trips this can cause an issue, IIRC this was introduced with the MK2 and not on the 150's anyway (i'd double check this, i'm running from memory here)
Only a few people have had injector, dual mass flywheel or diesel particulate filter problems, but they're no where near as common as the scare mongers will have you believe.
The Injectors issue - There was a bad batch of injectors that went into the Mk2s, however this is a FREE warranty fix.