We stayed at the Dusit Thani for two nights. Check-in was smooth and with an absolutely professional attempt to sell us an upgrade (which we didn't book) and unique Thai charme.
Our room type was a Deluxe King and absulutely sufficient for our needs. It was tastefully furnished, spacious, had an extra comfortable bed and a ok-sized bathroom with tub and shower curtain. The amenities you are given are absolutely great: apart from shower gel and the usual things, there were also two sets with toothbrushes, a razor set, a comb...
Breakfast is extensive and all food served fresh and delicious. The restaurant itself is lacking a bit of special atmosphere, unfortunately. It is located on the ground floor and made the impression of the usual cookie-cutter five star breakfast and buffet lunch dinner restaurant. It's not that it is not furnished nicely - it's just nothing to write home about.
Location is great, the skytrain station is just outside the hotel. The Patpong Night Market is within walking distance (be sure to haggle when buying something....) and Lumpini Park is just accross the street.
All in all, i'd say that the Dusit Thani is undoubtledly a very good choice as a business hotel in the Silom area and can also be recommended for leisure travellers - though there surely are more "special" hotels in Bangkok.