I use six different banking websites. In order from best to worst:
Halifax - 6.45% to 5.01% across my various accounts
Good layout, showing all accounts and their balance up front. Facilities for everything you'd expect from a main branch: everything from viewing previous statements to applying for an overdraft or another account. Interest rates clearly shown or linked. Easy money transfer in and out (with a current account). Simple log-in with memorable rotating question. Standard SSL certificate.
Egg - 6.05% AER (might be bonus rate)
Good layout of main screens. Interest rates clearly linked. Does not support deposits without a debit card, and address book system is hard to use. Longer, but straightforward log-in without rotating questions.
EV SSL certificate.
ING Direct - 5.15% AER
Log-in requires remembering a long customer number (supplied on a bit of card), a 6-digit PIN and a memorable date. Has an irritating dancing key-pad to thwart keyboard loggers. Otherwise, good layout and very easy to use. Occasionally fragile in Firefox when they re-work the site. Money transfer in and out via BACS. EV SSL certificate.
Sainsbury's Bank - 6.00% AER
Log-in appears straightforward, but uses ridiculous rotating questions (What's your memorable singer? What's your memorable name? What's your memorable place?) with stupid length limits. You can unlock the site without ringing up just by being able to answer a secret question anyway, so there's really only one password. I hate this log-in process with a passion. Budget web-design and tricky money transfer. Deposits must be made from a current account. Very limited facilities. Overnight transfer to Halifax accounts with no loss of interest. Standard SSL certificate.
Bradford & Bingley - 1 year Ebond, 6.50% AER maybe?
Painful to apply for - required a cheque FFS! Letters and documentation are ambiguous, because they are used for two types of accounts with vastly different terms and conditions. Log-in requires an alphanumeric account number found on a bit of cardboard. Severe restrictions on password length and complexity. Interest rate is not obvious at all -- in fact, without digging through the paper records, I can't find out which eBond issue I got by looking at the website. Can't really compare money transfer facilities with this account. EV SSL certificate.
HSBCSite doesn't seem to respond in Firefox (Minefield build). Log-in requires account number found on a bit of cardboard. I couldn't actually log-in to write this, because I've forgotten the security number (again!). Application process required exchange of identity documents by post, and by the end of the process I'd nearly lost the will to live. Money transfer facilities painfully limited. Avoid -- I haven't touched it since I opened the account. Standard SSL certificate.
Hope these comments are helpful to someone.