There is plenty to complain about with Virgin; their prices and price increases, customer service, slow DNS lookups, but I have generally found their infrastructure is mostly reliable.
It does go down and get flaky occasionally. It is more often up and close to advertised speed but like most I remember the glitches and lost hours more than I do the weeks of it working as expected.
Had one such glitch about 11:30am yesterday but no real problems.