For starters, travelers should note that Derry is still a very sketchy town. It has not yet experienced the rebound that Belfast has from the "troubles" (as the locals call it), and the "peace lines" (giant fences separating Catholic and Protestant communities) are rather disturbing. Sunbeam House is extremely convenient to the middle of Derry and is in fact the ONLY B&B in the area, but as such the neighborhood just isn't nice at all. There is a parking lot around back, but I wouldn't leave anything of value in the car. I've lived and worked in DC, NY and Chicago, so I was comfortable enough, but I wouldn't recommend walking around alone or late at night. Just be smart, and save your nights on the town for Dublin, Galway and Belfast (the city shuts down pretty early in any event).
That said, Derry should be part of any trip to Ireland and you should spend a couple days here. It's the best place to get a grasp of the history of Northern Ireland (both old and recent), and you should definitely book a walking tour of the old city.
As for the Sunbeam House, it's very quaint although a little rundown (which makes you feel at home in Derry!) Go there not expecting much and you'll be fine. The hosts are pleasant and everything is clean and comfortable enough. Breakfast was standard fare. The location makes it the best choice by far, as everything else is adequate.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.