Well I bit the bullet and bought a set of hf2's. Review below..
Initial impressions: Very pleased with them for $220 AUD. Very crisp with wonderful clarity in the mids and highs. Lows are also very well controlled, but lacking in punch and extension. Not the same level of bass response as my Westone UM2's (but I was expecting that from a single balanced armature IEM compared to the dual drivers in the UM2s, and won't complain too much at less than half the price), but the mids and high range have incredible accuracy for the price. Nice wide soundstage for IEMs at this price, but not as wide or deep as my UM2s.
Build quality is excellent. Soft touch plastic is used on each earpiece and the cable. Feels like a quality product, and what you'd expect for the price. The carry pouch is very good also. The come included with the excellent triple flange tips in 2 sizes (blue are for smaller ear canals), and a pair of foam tips that are a bit nasty. Spare wax filters and filter change tool included too.
The button on the mic works exactly the same as it does with the standard buds (click once to pause music, twice to skip forward a track etc). Haven't had any phone calls with them yet, so can't give any idea of call quality. Microphonics are pretty bad compared to the UM2's, but the microphonics of the hf2's are reportedly better than the ER4P/S. Something I'll probably get used to. Use of the shirt clip is pretty much essential if you're going to be walking around with these alot.
Early days yet, with only a few hrs use, but I'm very happy with them and think they're very good value.