I think 7 million is a bloody good start, considering that BB had a bit of competition from Celebrity Love Island, and the Kumars. Also, the advertising campaign this year was no where near as big as last year. Plus, as it was so hot yesterday, lots of people would have been out enjoying the sun. Considering these, factors,7 million is very impressive.
So far, things are looking good this year. At the start of last year, so many people hated the housemates, but there's not as much bad feeling this year (although there is a little). All the newspapers seem to have taken well to this years show too.