For the price, size, and stated amenities, Patumwan is one of the best buys in Bangkok. That said, no two stays are alike. In some rooms, the beds are good; in others, the beds are not. In some rooms the air con is great; in others, it hardly works. It's never ever the same stay twice, and one outstanding stay can be followed a week later by a stay that makes one consider never staying there again. It's not that that I've ever been angry or upset with the Patumwan, but when it's comfortable, it's a fantastic value, and when it's not, I simply would prefer to pay more for a better and more consistent experience.
I tend to be a fan of the Patumwan, perhaps because of a throwback to the backpacker in me (although this is not a backpacker hotel). I can be adaptive. That said, as I get older, I need my sleep and a reliable and comfortable place to stay, and this isn't always that. There are a number of rooms -- probably the majority -- that are taken by longer-term tenants, so the availability varies widely. I've never had a problem reserving a room, but then again, I book in advance. Arriving without a reservation can be hit or miss. Also -- I must warn the reader -- that they sometimes make mistakes with reservations. They take the reservations down, but then fail to book it out. This has happened to me more than once, but fortunately I've caught the error in advance -- always stopping by in person when I know I'll be staying there at a later date -- to make sure that my email or phone reservation was, in fact, put on the calendar. Lightening has struck the same place more than twice in this respect. There is a better-than-passing chance that one's reservation won't be properly booked. It's not 50/50, but it's also not a 1-in-100 event either. I'd say it happens a good 20-25% of the time. I once stopped by while in Bangkok to check on two different friends' reservations, both of whom booked at the same time. They had one reservation booked but not the other.
Keep in mind that because the Patumwan caters to a long-term client, this isn't the place to give you advice about sights to see or places to go. They don't generally have information about tours (and I don't go on any tours anyway) and aren't super great about knowing specialty places (bars, restaurants, etc) that might appeal to a foreigner. I once surprised a girlfriend with a stay at a famous five-star hotel for her birthday, and I wanted them to write in Thai the name and address of the hotel -- so that my American girlfriend wouldn't be able to read it -- that anybody in the hospitality business would have known. They had never heard of it. It would be like a concierge at a small hotel in New York not knowing about the Marriott in Times Square or the W Hotel near Wall Street (hard to imagine). They were more than willing to help, but their help was, in this case, useless. What they were helpful in doing, however, is to get us "thrown out" of the hotel due to a feigned overbooking so that I could surprise my girlfriend with this luxury 5-star hotel on the river. It was one of my greatest coups ever, and I couldn't have done it without their gracious help.
With all of my reservations about the Patumwan, why do I give it four stars? Because for what it is, it's great. It's great value with some lovely people working the desk (the man is always grumpy), but you have to be willing to anticipate their shortcomings and go with the flow. That said, I don't always stay at the Patumwan when I come to Bangkok, particularly if I'm arriving late and I don't want to chance them screwing up the reservation. I might book a stay while I'm already in Bangkok for a later date when I'll return. In fact, despite that my girlfriend and I transited through Bangkok several times during our trip to Thailand, we opted to stay elsewhere to guarantee our comfort. That's a nice thing about Bangkok: one can always find a quality hotel -- and sometimes a luxury hotel -- for reasonable prices in one searches. It's not the 1000-1500 baht room that the Patumwan offers. Rather it might be 2000-3500 baht, but by our Western standards, it's quite reasonable.