I was pleasantly surprised by the Hotel Ikon. It is an old hotel, and doesn't have many amenities. But the rooms are clean, the beds and linens clean and soft, the wifi was good, The staff was friendly and helpful, and the location is fantastic, just a block off Powell Street and a couple of blocks from Union Square.
If you want a clean, no-frills hotel in a great location and a good price, the Hotel Ikon is hard to beat.