I recently pulled out my initial investment by using Kraken (in EUR via SEPA bank transfer, so my experiences only apply to that), and it was super-easy and fas

I recently pulled out my initial investment by using Kraken (in EUR via SEPA bank transfer, so my experiences only apply to that), and it was super-easy and fast. Deposits usually took 2 days to clear; the withdrawals took just one business day until they showed up on my bank account. So it was even faster to get money out of it than to get it in. Kraken's trading engine is utter crap, but as an on- or off-ramp for fiat it seems to be worthwhile. I guess for USD it should work just as well, though GDAX/Coinbase seems to be the most-used on/off-ramp there.