We stayed at the place for two nights 24/,25/3/07. Can recommend room 400 & 401, top floor with balcony, spacious and excellent view (USD35/ room/night).
Breakfast (in price included): not great and not surpisingly as the kitchen looked like the devils cave. As other guests, we went elsewhere after the first experience.
Place is undergoing major renovation with possible other nice rooms in the future (I suggest the kitchen be part of it).
Hotel offered airport pick-up for free, which was fine. But barely seated in the car, the constant nagging from the driver to hire the car for the other days as well became unnerving. Hotel also offers travel services and the hassling of some of the staff (others are very friendly and helpful I must say) to use their travel & transport services continued - be polite and ignore it. We hired the taxi to Siem Reap elsewhere in the end, a better car and 1/3 cheaper.
My top blew off at check-out when I received the bill including an extra pillow dry-cleaning charge because we were found guilty of having dirtied it beyond the power of a normal washing. I was sympathetic with the staff to the point that I did agree that not all guest have proper manners and do misuse property if not their own. I do however not belong to this group. The finally deleted this extra charge (staff claimed that they have to pay such cleaning from their own pocket if guest does not pay it) as the yellow staining they claimed came from our use was actually allover the inner lining of the pillows (I undressed all pillows I found in the room and lined them up).
Conclusion: Go for the good rooms, check the pillows and if thinking about food check the kitchen as well.
Ah yes, there is a lift, internet is free and the drinks cold.

I stayed at the Riverview 3 times: July-Sept 2004, Oct 2004 and July 2006. All 3 times, I stayed in the spotless, air-conditioned room with own toilet/(cold) shower, and cable colour TV, for US$10 per night. There is no longer a restaurant on-site, but there is an Irish-owned pub next door with pub food, and a very good Cambodian restaurant (US$2.50 all you can eat lunch buffet) around the corner. Management can also provide laundry service, and book tours or bus and plane tickets (I have used all these satisfactorily). Now there are many "tuk-tuks" next door: this means (1) you can get anywhere you want to go to in Phnom Penh, relatively safely (more safe than the back of a motorcycle) but (2) the drivers do hassle you when you come out to take a ride, as near many hotels and guesthouses in Phnom Penh. The area, in front of the Post Office, is more residential and does not have that atmosphere of the masses of bars and expensive restaurants "down the Quay". The site is also across the street from the dock for boats going to Vietnam. The owners are a young couple, Sunny and Kaing, who have always been eager to help with anything I needed to succeed in Phnom Penh: their English is not perfect but if you are patient you can communicate. By the way, the address on this site is wrong: it is 87 Sisowath Quay and the e-mail address is riverview_guesthouse@yahoo.com.