I've stayed at the Hilton Islington 7 times this year. I've had a success rate of about 60% on upgrades. Problem is I stay during the week and it is always full. I suppose if they can sell an Exec room then they would rather do that than give it away. There is not much difference in the rooms in any case. The hotel is an ex-Stakis and therefore build to their design and business model. The exec rooms are slightly bigger and have water and chocs. There are some buisness rooms that are like suites but the living area has an office with a sofa, desk, PC printer and full (free) internet access.
The area around the hotel is excellent. It is much less "touristy" than other areas in London. As it is a very afflunet area there are many, many superb restaurants. The competition keeps prices in check though.