Bitcoin isn't deflationary yet and won't be for decades at least.  Technically, it won't be until 2133, when the block reward drops to zero; but in practice it may turn deflationary at some point in the middle if the loss of bitcoin addresses exceeds the creation of new coins.  Presently, Bitcoin is still inflating at over 40% APR (decending) and will not drop below the common 'target' inflation rate of 2% APR until about 2020.  So regardless of where one lands on the 'deflationary spiral' debate, it has no bearing on why Bitcoin should or should not be used in our lifetimes.  Our grandchildren might have a real reason to have this debate around 2050 or so.  The 2030 date that so many articles throw around is just crap.