I do think there are some aspects of bitcoin that limit its use as a medium of exchange (transaction times, current lack of stability), but I don't think its the deflationary part.
This doesn't really feel the same. You might use USD to store value because you know that it's value isn't going to fluctuate like crazy from month to month or year to year. So if you can afford to feed yourself today, you can still feed yourself tomorrow. You're still spending your money.
No one I know with Bitcoin spends it, with the exception of a novelty purchase of beer. And why would you, in 4 years the value of bitcoin increased over 10 fold. You'd be stupid to ever spend it while this trend continues.
Noted, and I tend to agree with you on that point.
> You'd be stupid to ever spend it while this trend continues.
For sake of argument, assuming you know this trend will continue you'd be stupid to not put all of your money into it. At which point, you'll ultimately need to spend it to get things you need (whether you're spending it on purchasing other currencies, or spending on the actual goods). Unfortunately, we don't know the trend will continue or if it'll reverse or if it'll level off.
It could even be expanded to include inflationary currency in a country where hyperinflation is occurring. People will hold on to USD or some other currency as an investment because it'll be worth significantly more tomorrow than whatever currency the supermarket down the street accepts.