Unfortunately I've not really had it long enough (2 months/3200 miles) to fully comment but I have some observations already.
Regarding the car not a lot of complaint really, it's pretty good, its comfortable on the bumpy A and B roads I travel, looks good inside and out, handles quite well though highspeed stability (>110mph) not as good as some cars I've had, probably just a geometry thing Fiat are notoriously bad at getting that right out of the factory, I've not took it to get checked as I'll be switching out the setup to something that's likely to ruin its currently decent comfort level for more of a trackday focus.

I ran the car stock at Cadwell park though and came away very happy with its ability in stock trim to be fair, body roll is minimal, nose dive underbraking almost non existent, bit of wobble from the rear I'm sure better dampers would tidy up, brakes were strong with no fade, I can see no reason for me to change them even when I up the power, had a similar setup on a few cars in the past and that size discs with those Brembos can cope.
Not had any real issues, gearbox was very ropey initially and have read a lot about issues with the Alfas running the same box but now I've done a few miles it seems slick, does make some noise between 1st/second, again not time to take it in for investigation, but the change is fine no notchiness, just noiser than i'd expect, it does concern me a little and might be one reason for me to go for the esseesse kit and leave it there whilst a bit more time passes and I can get a feel for whether there is a fault or early niggles, either way I'll want that warranty intact.
Regarding gearing, its a bit short geared, 1st three gears are a bit like a turbo diesel, its so short that the revs rise so fast, at first I thought it was an early rev limiter but actually it seems as though the rev counter is too damped and can't keep up with the engine

I can see myself hankering after a final drive mod once I start to really up the power, looks like there might be options on that score.
Really impressed with the MA engine considering its capacity it's quite tractable even off boost, the fuel economy leaves a lot to be desired considering my old Alfa had worse figures at 32,42,53 vs 34.8,47.1,58.8, the Alfa would average 45 and I could granny it to 55-60mpg, the Abarth needs to be driven quite carefully just for 40mpg, so despite the diesel like gov figures it is both slower and less economical than my old diesel

it is a bit more fun to throw around than the diesel though and barely scrubbed its tyres on the track where my diesel would have mullered a set, its still early days though, the Abarth has been steadily improving on the consumption front from the early 30s to early 40 its doing now, Economy really drops off a speed in some part due to gearing.
Poor sales are obvious, there is stiff competition in this sector, the Evo Abarth probably has the lowest power in its sector, the lowest performance stats on paper, plus some of the competition can be bought cheaper due to greater discounts available (Clio/Corsa are performance bargains), if you factor in the price of the essessee kit you are even nudging the discounted prices of motors in the next category.
Abarth have not done enough to nail any headlines really to justify its pricetag, the target market for this sort of motor is the younger driver, the ones most impressed by paper stats, Abarth have lost on this score.
Depreciation is what it is, first year drop is always a killer when your car is not the hot ticket fashion item that say the 500 is, end of the day despite a pretty decent facelift its still an old model, still its depreciation is likely to be no worse than others in this sector though but really if depreciation is a factor to you then perhaps an Italian motor is not for you, old biases are hard to shake, most people are still wary of Italian motors, drop like a stone after 3yrs. All that said if you look you'll find similarly hit motors in this sector, even the benchmark Clio has the odd motor that has dropped 5k despite all the headline grabbing attention it gets.