Currently with Netspace. Was with Exetel until they started blocking my access because of bogus spam reports from the worst ISP on the planet - AOL. I haven't had any problems since blocking AOL users from using any of the contact forms on my site. Never gone down in 9 years apart from the short period caused by AOL.
(upgraded from ADSL1 to ADSL2+ yesterday with no noticable downtime)