I think you are very wise to do your research in advance.
It took me almost a year to finally decide to buy my 147. Mainly because I am a very picky but inevitably partly because of my concerns regarding the perceived reliability.
If you scan the forum you will no doubt read plenty of horror stories regarding reliability but conversely there are countless who experience little go wrong with their Alfas and a trouble free live.
Realistically, you need to walk into the experience of owning an Alfa with your eyes open. They need to be loved and regularly maintained in order to ensure that they give the best back. There are of course some features which are typically Italian and you can expect the trim to fall off and the electrics to ocassionally be a bit haphazard!
I think the 147, as a fairly recently engineered car, is reasonably reliable although it doesn't score well for reliability in Top gear style polls (not sure how much of that is as a consequence of crap dealer support). However, have a scan through the 147, 156, 159 technical forum. This should give you an idea about common problems and the cost of resolving them.
There are Buyer's guides available on the AROC website and on the Alfa workshop site (http://www.alfaworkshop.co.uk/alfa_romeo_147.shtml)
Not sure of the general running costs of the 1.6 but you would certainly need to consider the relative servicing costs (main dealers outrageously overpriced but then aren't they all!). There are plenty of recognised and well recommended independant specialists to chose from.
There are well known servicing requirements which you might want to consider, particularly when buying a 4-6 year old like mine. Note that the Cam belt must be changed well ahead of recommended frequency and there are twice as many Spark-plugs on a twin spark just to add to the costs. Apart from that servicing costs shouldn't really be any different from other similar sized models in it's class.
Anyway, try the forums as they are a goldmine of advice and information (mostly) and hope to see you become a regular on here very soon.
In the end I decided that I was going to take the risk of having some problems because I loved the car so much.
Its a pleasure and pain thing!