Well, you could have an extra set of batteries in case the ones you're
using run out of steam. Wouldn't cost that much. You could buy a 150
and *several* sets of rechargeables for what you'd spend on an E1.

$500 is too much for a portable receiver. The SW77, before it was
discontinued, also cost around $500. That doesn't show that the E1
isn't overpriced, but simply that both the SW77 and E1 are/were
overpriced. Yes, the E1 has a lot of "features", but you're asking for
disappointment if you base your buying decisions on long lists of
features. (Features are relevant, of course, but they don't guarantee
good performance.) No matter how many features you tack onto the E1,
it's still only a portable receiver. A really good portable receiver,
no doubt, but if you have $500 bucks to spend, it's time to walk out of
the portable aisle--unless you have money to burn and don't care about
bang for the buck.