It has changed a lot since 2008, bar street has all but gone, many of the bars have closed and if you walk along there at say 11 or midnight, instead of bars there are now gift shops with stalls out the front, there still are a few bars but these are much quieter.
The place has changed in that now it is a more middle aged type of visitor and they tend to drink around the centre square, 5 years ago it was all about youngsters in bar street and then on to clubs, nowadays the clubs are still there but much quieter.
In many respects this has actually made Kardamena a better place as there are not the groups of youngsters around drunk and shouting, the restaurants and centre square have flourished as a result.
There are still some 18 - 30s there but they tend to be in organised bar crawls and get "marched" along the front to bars such as Starlight beach bar etc and then onto Starlight club etc, Starlight tended to open a few nights a week and was quite busy on the theme nights, but when I say busy I mean perhaps 250 / 300 people, where as in previous years there would have been 1000+ in bar street at midnight, this is now probably 100 at most now.
In summary as a place for youngsters / 18 - 30 I would say Kardamena has definately "deteriorated" where as for all other groups it has got better.
For 17 year olds the places to go are Napa, Laganas, Malia, or Magaluf or Kavos, (Faliraki is dead before that's suggested as an alternative) and of those my suggestion would be Laganas in Zante as apart from anything else it is a strip of bars and many of the bars have clubs behind, so you can have a drink in the bar and then move onto the club behind, there are also far more clubs in Laganas than Kardamena (even at it's height)
Malia is pretty busy and has many bars & clubs but if you are worried about fights (and bearing in mind it's your first holiday) I'd probably suggest you give it a miss, it can get quite "punchy" at times and we saw a few incidents when there in June this year.