Look at the comments to this blog entry
Is HBSC Taking Advantage Of The Float? An Experiment » My Money Blog. HSBC's transfer slowness seem's to be due to their choice of using CashEdge's 3-day transfer system.
Here's HSBC's reply to my question "Where is my money during bank2bank transfers:
Bank to Bank Transfers are ACH (Automated Clearing
House) transactions and go through a clearing process
through the Federal Reserve. Once the money is debited from
the sending bank, it will take approximately one business
day to reach the ACH Network, approximately one business
day to be processed through the Network and approximately
one business day to post to the receiving bank. As the money
is not in the account at throughout the transfer processing
stage, there is no way to earn interest. We apologize for
any inconvenience this may cause.
I guess CashEdge is earning interest on the float as its cut for processing the transfer. As big as HSBC is you'd think they could do better!