well is it balanced, erm sennheiser think so, its failrly balanced but still a bit bass heavy, it can dish out great big dollops off bass easily but still got great mids on them and nice highs too.
the buds well i wasnt huge on them, but those ebay things i found to be amazingly good and super cheap too, so id say if u buy the 7 buy some of those tips too, even if u dont like them its like waht £2 if that.
isolation it isnt great, but better than the ex500 you were thinking about. i mean isolation isnt terrible but if you are coming from other high end IEM's most of them have lots more so it feels lacking. if you are coming from say cx300 you want notice much if any difference. if your coming from ibuds youll think its great.
cable is maybe the best cable ever and strength wise ive not really tested but its coated in kevlar so im thinking it should be fairly strong.
comfort wise with those ebay tips i find the 7 very very comfortable, could and have worn it all day long wiht no problems, the things are freakishly light. like disturbingly light.
hope that helps