First: happy car owners, of any make and model, very rarely actively post in forums as most people do this only to find answers to an exisiting problem!!! So the negativity is in the nature of a forum.
This means that the vast majority of Forum members is experiencing some sort of problem with a car, otherwise they would not be here. There are a few exceptions of course.
The remaining vast majority, which in real life, represents the 99.99999999% of the owners, will never view or post in a forum.
You will always find negative comments about any car: e.g. you will find many negative posts against the Punto as well, but there are millions of Punto owners in Europe with very little or no problem at all, you simply do not know about them.
I have been myself a Punto owner for a few years, my wife the same and my father (3 Punto in total), and we have never had even a glitch with these cars. We haven never posted a message here neither.
The same for Stilos: of course you will always have a number of cars which can have a tech problem, especially due to the complexity fo more recent cars like the Stilo which are packed with electronics and sensors.
I know many people owning a Stilo now, more in Italy than in the UK, and all of them had no issues with their car: of course they do no post here, nor they know this forum exists. They just enjoy the car.
If you like the car just go for it: the chance of finding a problem is very low, the Stilo is generally extremely reliable and a few exceptions should not change your mind.
Do not forget that any Make and Model can have problems including cars with higher prices, but this does not mean they are all bad.
Somebody here has been very unlucky, you will read of people (very few really!) with several faults at the same time or similar horror stories. These fortunately are rare cases and can happen to any car owner including Jaguar, BMW or Ferrari.
I am absolutely sure that the vast majority of Stilo owners is extremely happy with the car: but they are not on this forum of course.