Yes, the trains run right in front of your window, and there are quite a few of them - freight trains, ICEs, S-Bahn ... but if you close the window it is not too bad. Noisier was the fan in the bathroom! Room 414 was an especially nice corner rooms with two "wintergardens" (conservatory, well, a kind of glass niche). The bathroom was new and clean, the towels old and shabby, no shampoo and cheap shower gel in a little plastic sachet. That wasn't really up to 4 stars. Breakfast in a basement room with a very friendly look, silver candlesticks on each candle and smoking prohibited. Breakfast choice quite alright. Funny: Order fresh-pressed orange juice or champagne or fried eggs and pay for it at check-out. Easily reachable with public transport (not just train, also tram and bus), not far from center. At EUR 73, I thought it was fine!

Stayed at the Hotel Mado in Koln a couple of weeks ago on a weekend visit. Found the hotel value for money and well located.
Never found the railway line beside the hotel to be a problems and certainly didn't see any drunken students.
Would agree the hotel is not in one of Koln's best area but I didn't feel intimidated walking back to the hotel late at night, in fact I stopped off for a few more beers in the local pubs.
You get what you pay for and I would say its value for money.

We have just spent two nights in this hotel but moved for the second two days of our visit. Whilst the hotel was modern, well equipped and furnished with a nice, very quiet sauna and "wellness" suite and served excellent breakfast the unbearable problem was the noise of the trains which passed our window every few minutes. Three railways lines converge out side the hotel and the noise was unbearable - we could not shut windows as it was very hot. it would be better in colder weather. the staff were very helpful and changed our rooms for th second night but it was still not possible to sleep much.
The hotel is in the university part of town which meant that it was a bit threatening walking around the streets at night and impossible to get a drink in the hotel lounge bar as it was absolutely full of young students until 3am! We had to pass a young man urinating up the wall outside the hotel and alk over a lot of broken bottle and drunken youths to get back into the hotel which was unpleasant.
Summary - a good qualityhotel, in a bad area and okay if you take earplugs!

We stayed one night at Hotel Mado and liked this hotel a lot. It was extremly comfortable and the room was very large, very clean and nicely furnished. Breakfast was wonderful with a great variety of food which was very tasty. The staff was friendly and helpful. We paid about 70 Euro for one night (it was a weekend-deal) and I'd say the hotel was very much above average for that price. I'd stay there again anytime!