The Xscapes arrived today. I generally find that my perception changes during the first week or two of use, maybe burn in is a factor or possibly just getting used to the signature, so don't take these comments too seriously, but it's worth making some preliminary remarks.
First off, the response isn't as flat as I had expected. I think the upper bass is a little forward, and there is a dip in the low to mid highs. In fact, certain parts of some music can sound muffled when there are no high highs in that part. Orchestral music is a good test. I played Chesky's Vivaldi's Four Seasons and also some Bach, and the bass instruments sounded very 'bloated' and muffled, and there was a resonance that bled into the higher frequencies. The psy trance that I listened to lacked clarity, but hard trance was pretty impressive. Isolation is not great, but is certainly sufficient for my requirements. Having not used IEMs previously, I'm not sure how much isolation can be expected.
In spite of these comments, I'm not unhappy with the purchase. For under a hundred bucks, they're certainly not bad. What I have to compare them to at the moment is a $300 pair of open headphones (the AD900s) and a $1000 pair of active studio monitors (the TR-8s) so I may be a little biased. As I said before, these are just preliminary comments, and I'm optimistic about how I will feel about them once I get used to the sound signature.