I have lived in a studio in the past. Can't afford one in London though at the mo....
Studios are pretty cool IMO, if you have one in a city centre (affordable on a graduate salary in most cities other than London).
They are really easy to look after and keep tidy and it is good to have your own zone to set how you want, have access to kitchen/bathroom/TV or whatever on your terms and not have to wait for other people. Also it's nice to have your own zone where you can do what you want and not worry about what other people think.
I never found that loneliness was an issue in mine. I worked fairly long hours and I often went to bars etc after work with people so I wasn't sat around my flat lonely. I quite valued the time I had by myself because I got to do the stuff I wanted to do. I found it was much easier to chill out after work in the evenings when I was in a studio than in a flatshare because I could come home, cook, then read / play football manager / watch films and go to bed and have had a total break ready for the next day.
In a flatshare I get home from work and my housemates will decide they want to do something and drag me out when I'm tired, or one of them will be ranting about the kitchen/bathroom being a mess and demand everyone goes and cleans up. When I lived in a studio by myself, the place never got that messy and only ever took about 10 or 15 mins to scrub down the surfaces, but when I live in a flatshare I always find there's somebody in the house that wants to cook really greasy and messy food, make a big mess and then leave it and then randomly start ranting that it shouldn't be just their responsibility to clean up etc.
The other big advantage with studio living was I never had any issue with bills. Bills came in, I paid them. Didn't have to go through the rigmarole of chasing housemates to get their share of the bill or have the endless 'negotiations' from them (eg "well I was away for 2 weekends so I should pay less for this bill").
Oh and one more thing I noticed, I found I got a lot more sleep when I lived on my own. Not because my housemates are necessarily noisy, but because when I live in a share I always find there's somebody up late who wants to talk and end up still chatting to them at 1am, whereas in a studio I could get in bed at about 11, read for a bit and then just put the book down when I was tired and drop off.
Personally I think studios are a pretty cool way of living as a young professional but I know they are not for everybody. If you have a massive wardrobe of clothes and loads of stuff you might find them cramped for space as you don't have spare rooms. Also socially, as you don't have housemates, you need to have a social circle through work or other friends. Some people like living in houseshares as a way of having a close circle of friends, which when you are out of education you don't automatically get put around you like you did in the past.