Udee Bangkok is a great hostel - although you won't like it if you want to really be in the heart of the city.
Our double room was nicely decorated, clean, modern and the bed was comfortable. The wifi was super-speedy and the staff were always friendly and helpful.
The breakfast is self-service - find some bread in the kitchen and make some toast. But refreshingly it is included - and not an extra 100baht a day that so many hostels make it.
Unfortunately Udee Bangkok is in a bit of a nothing area of the city. There's nowhere really to eat nearby aside from a shopping centre which has drab but very cheap dishes. The sky train is only a 10-minute walk away and an efficient service. However, the network is not connected to the whole city - and won't, for instance, take you anywhere near the Khao San Road. You can get there on the bus though.
If you don't mind this, Udee Bangkok is great. The basement bar area with a television is pleasant and the roof garden is very nice. If you want to relax here with a drink it is the perfect place - and the hostel sell beers for a price almost as low as the 7-11. With cheap beer so close to home we happily did without a decent bar nearby.
Udee Bangkok sent us an email asking us to review them so they know how they can improve. We clearly haven't helped as I can't make any real suggestions - the hostel is great, but it's a bit out of the way.