I have two of the 3000 and two of the 4300 Zippy-K packs. They get a bit warm (120 or so) but so far they're still taking plenty of capacity, more than advertised. No complaints for as much as I paid for them.

I sent an email to Hobbycity about the lack of 2s Zippy-R packs now. They pointed me to their Rhino lipos which seem to have similar specs but still no 2s. They have promised more capacity, however...