In reply to jockster:
Hi Simon,
I've got a pair of Binatone Terrain 750s (Also come in a 4-pack)
They've been pretty thoroughly tested; work fine up to 5km as long as there's no Gabbro hills in between the two of you (I'm looking at YOU Carrock Fell), got a patchy signal up to 9km over hilly ground, 8km worked fine from different peaks.
As for durability; they've been kicked about, thrown in bags, clipped to harnesses, dropped off Tremadog (turns out you SHOULDN'T clip it to a harness) and left in a stream for a bit - and they're still going great!
Battery needs charging every night if they're left on all day. Comes with NiMH packs, but takes standard AAA as well.
You can also listen in to two channels at a time - good for supervising groups.
Hope that helps,
George