|Various types of directories are included in the collection|
Apart from that cautionary grumble, I think this record set will be lapped up by researchers, whether their ancestors were born and raised in the wider capital area or, like so many over the years, migrated there from Ireland, Scotland, Wales and the English countryside.
I've already had a profitable search in the collection, coming up with a new address for my paternal grandfather during one of his brief post-war sojourns in London (and even more exciting, Google Street shows the building to still be standing), and a bookbinder Santry living in Borough High Street in the 1830s and 1840s who needs further investigation.
There are several types of directory included in the collection:
Street: listing of residents, businesses, and tradesmen according to street address
Commercial: includes businesses, but may also include private residences; generally an alphabetical listing of traders
Trade: not just for businesses, but anyone with a recognized trade or profession; an alphabetical listing of trades and businesses
Court: lists wealthy residents and government officials
Post Office: listing of householder's names and addresses
Many of the later directories include private residents, and they're not all wealthy or prominent members of the communities, either.
The collection is indexed, but Ancestry's search page also allows you to browse the individual directories by name. If you have searching for ancestors in specific places at specific times, I'd suggest you check the names of the publications, and their dates of publication via this browse facility.