We have negotiated our rates down, but I think it depends on what sort of transactions you have - the rates might seem high if you are making many transactions of relatively low value items for example. We sell used cars, so transactions are not exactly frequent and values are in the £000's.
We have tried other companies over the years and whilst they were cheaper with their fees, 5-10 days to receive our funds was excessive. If you decide to switch, make sure the card company is working together with your bank. We use Natwest and the company we tried last year used Barclays, therefore, so they claimed, funds would have taken 3 days to reach us had we been Barclays customers and not the 10 days it took one of the transactions to reach us due to being with Natwest.
It was at this point we cancelled the contract and went back to Worldpay and negotiated a better deal at the same time.