people only invest in so they can get rich quick
This is utter bullshit. Some people may be speculating on a short term increase in exchange rate, but I doubt many.
can't use to pay their bills
isn't any more anonymous than cash
Cash can't be transmitted digitally.
and constantly deflates
Nope, the supply of bitcoins is constantly increasing (around 7,200 per day).
if you actually USE bitcoin to sell products, you have to re-adjust your prices every 2 days because the value changed so much over the last 48 hours
This is only due to the demand for bitcoins outpacing the supply, causing an increase in the exchange rate. The same thing happens in any market that spans more than one currency.
This is only a problem while businesses expenses cannot be paid with bitcoins and/or the demand for coins exceeds the supply. Once both of those conditions are no longer met, the exchange rate will either equilibrate or will no longer be necessary to determine price denominated in BTC.