It didn't seem to matter (last night) which wallet I was transferring BTC from/to. It was oddly slow. The usual excuse of "the network is saturated" doesn't fly, though, because numerous blocks were far smaller than the typical "999827 bytes" (within a stone's throw of the 1MB maximum). If the miners were working non-stop full-tilt, then why were a sizable fraction of the blocks only 400k-600k? That implies that the mempool wasn't "full" (with backlogged transactions). Why else would a miner NOT pack more transactions into a block they're working? This was not limited to Coinbase. I had the same delays transferring from my Android wallet to Kraken, and from Coinomi wallet to Electrum.