In principle you should see higher inflation and a falling currency. However this policy (aggressive buying of all kind of bonds) has been persued by the Europeans and Japanese for years and it haven't really caused a collapsing currency or high inflation.
Some may argue that it suspends a natural reallocation of resources in the economy. And causes the economy to keep overallocating real resources into things like real estate and finance causing bubbles, malinvestment and zoombie institutions ultimately leading to lower growth.
However that assumes that you had a free market in the first place which you never really had.