I like the Conrad Hilton the best, and also the Mandarin Oriental. These are both in the Marina area. I have also stayed at the Marriott on Orchard Rd, and the Sheraton that is just a few blocks up from the Marriott. I found the Sheraton to be the worst.

The Marina area is nice, but not in the center of things like around Orchard Rd. However, taking the subway is very easy, and kinda fun.

M8