Our family (couple with baby and toddler) stayed in Kent Hall hotel on a Saturday night to attend a party nearby. As a place to crash it was absolutely fine, though I wouldn't have wanted to while away many an evening there.
The room was quite basic and smallish, but (with the exception of one padded chair) everything was clean and the beds were comfy enough. There were some unexpected extras like toiletries, a fridge in the room and a flat-screen TV with lots of channels. We asked for a room at the back and it was quiet, facing onto trees.
Beds were comfortable enough (not conked in in the middle!) and they have sheets and blankets not duvets. Ours was right in front of the window so I was woken earlyish by the light.
Rooms are arranged in groups of 4-5 on either side of the staircase so you don't get the problem of hundreds of guests traipsing past your room and making noise (maybe we were just lucky!).
We met about half a dozen staff and they were all friendly and helpful.
Breakfast was simple, with eggs & toast freshly prepared for each customer (no greasy buffet platters here); the only downside was a rather strong cup of instant coffee!
I would consider staying here again if I needed to be in the area.

If you're only staying in London a short time and money is not really important, then Kent Hall might not be as suitable for your needs as a slightly more expensive bed-and-breakfast in Camden, but if you're staying for a while, and on a budget (say, a researcher like be, using the British Library), then Kent Hall has a lot to offer:

1) Basic rooms, but with amenities you won't find at more expensive centrally-located hotels, such as a) your own fridge, for water bottles, snacks, beer, wine, etc., b) a decent-sized table that you can work on, c) excellent Wifi connection for a one-off five pound fee that's a great value and very handy. True, the rooms are basic, but they're cleaned daily and the hotel provides soap, shampoo, etc., as needed, plus clean towels.

2) Breakfast is included in the price. As some have noted, it can be "monotonous," but the staff try to mix it up, making eggs in various styles - omlettes, fried, scrambled, and so forth. For a little more variety, however, you can always try the Park Cafe at the south entrance to Finsbury Park, a short walk away, which offers an excellent full-on English breakfast for 4 pounds and friendly service. There's another cafe next to Manor House station that also offers breakfast if you're hankering for ham and sausage.

3) Neighborhood: Finsbury Park isn't a happening night-spot, full of pubs and clubs, but you can jump on the Victoria Line at Finsbury Park and be in Islington in less than 10 minutes, with no end of tapas bars, wine bars, pubs, and restaurants to choose from on Upper Street. You can also be downtown, in the tourist district around Covent Garden and Soho, in about 20 minutes via the Picadilly Line from Manor House, which is literally right outside the front door of Kent Hall and a one-minute (if that) walk to the right. Coming home late? No worries: there's a 24-hour shop open on the corner, and several late-night kebab places that will cure the munchies late into the night.

4) Convenience: If you're working at the British Library as a visiting researcher, you can leave the hotel at 9 AM and be at the Library, via Kings Cross station, with time enough to grab a quick cup of tea or coffee before the doors open at 9:30 AM. Need laundry done? The hotel doesn't offer this service, but there's a laundry at the corner that will wash and dry a fairly large bag of clothes for 8-10 pounds, with next-day service. There's also a post office by Finsbury Park Station for changing travelers' cheques, mailing items, etc.

5) Helpfulness: The staff are helpful and accommodating and friendly - you won't always get this at more expensive hotels in central London. The staff there will be very professionally dressed and often completely unhelpful. At Kent Hall, there's a relaxed atmosphere and the sort of flexibilities you often won't find at more expensive hotels.

6) Secure: The hotel front desk is manned 24-hours and your room is very secure. Using good judgment is essentially here, as elsewhere, but unlike the situation at a big hotel, you'll probably know who the cleaning staff are at Kent Hall. From what I could tell, the management was very careful about who they hired.

Some remarks on the neighborhood: Finsbury Park is a very ethnically-diverse locale, but certainly not dangerous. You're far more likely to have your pocket picked in Soho or Leicester Square. The ethnic mix of Finsbury Park - Turkish, Jamaican, Greek, Jewish, Pakistani and Indian, Polish, and now Spanish (and, of course, English) makes for an astonishing variety of cheap restaurants and a vibrant atmosphere. I was there during the recent riots, and the neighborhood was perfectly quiet while there was trouble in neighborhoods all around.

Note: The staff at the Manor House tube station are very friendly and helpful, and will happily sort you out with directions, tickets, etc., if you ask.

I would reccommend the Kent Hall Hotel for travelers on a budget who want something better than a hostel, but who don't want to pay for an expensive hotel.
The rooms are basic and a little shabby, but everything was very clean. The staff were pleasant and helpful and the breakfast was tasty and filling.
For some Americans the neighborhood might look a bit grimy at first glance, but I've stayed in that same neighborhood many times and always felt safe. Also, this hotel is so close to the Manor House tube station that the hotel can be seen from the top steps as you exit the tube station.

It's shabby and weird, but completely fine. I got a huge room at a single price. Non-functioning TV (I personally couldn't care less) and the room backed onto a building site, and the breakfast was pretty poor, but really you're not going to find anything better at this price. It was clean, safe, comfortable and had electricity.