In my experience (6 months worth of a JTD 115 ELX) I would say:
Cons - When they go wrong, boy do they go wrong.
I'm currently looking at:
(Mechanics and Electrics)
ABS Sensor,
MAF Sensor,
Speed Sensor(Fiat only Part),
Airbag Fault (Fiat only Job).
MPG is a dubious thing.
(Exterior)
Pain Oxidizes off wing mirror mounts (easy repair and only a few £)
Door Handle "bumpers" chip and scratch easily (mine look like a dogs chewed them - again, only a few £ each on ebay)
(Interior)
Upholstered in Tissue Paper,
General build quality is iffy, plastics fade, become brittle or just outright break.
If you have the two sunroofs, the seals constantly come off if theyre not regularly used,
The sunroof switch comes out of the headliner on a weekly basis (which reminds me to find the superglue)
Pros
They are even more practical than a date with a nice bird,
Great fun to drive,
Turn heads wherever they go,
Parts are inexpensive and easily sourced,
With the back seats removed, you have a Van with more than ample room.
Even the most basic of mechanical knowledge is enough to work on them,
I had mine mapped (150 ish bhp) and its fun watching TT's, ST's and MR2 Tbar's being left behind with an absolute look of disgust.
I would say do it.
I intend to have a little play and maybe go Euro with mine but I may just continue with a Sleeper....