I don't recall ever having expereinced smell or taste during a dream but I have a feeling that these functions, at least smell, are taken for granted and that's why we don't use them in our dreams. I do experience touch sensations in dreams though. I recall a dream where I was being held prisoner and was pushed from behind in an effort to get me out a doorway and onto a walkway and the sensation was very vivid. Some of the feeling dreams are very real. I have been shot with bullets and cut with swords and while it didn't feel as painful as it would have if it had been a waking experience it was still painful and of the same type of pain. I remember once I was dreaming that I was laying down and some nasty guy was giving me an injection into a vein in my wrist and it hurt and I woke up and my wrist still hurt. I have the same type of experience oftentimes with sex dreams, I will wake up 1/2 way to the point where I am aware of my room but the escalation of climax will continue while I am awake to the point of orgasm.

Smell is a clairvoyant ability just like clairaudience and there shouldn't be any reason why it couldn't be experienced in dreams.

Edit:

Just for the sake of information sharing I am going to add something about the sexual experiences because of the subtle aspect of their nature. I was reading other things in this particular forum and thought it a good idea to add this to this thread. I told that I sometimes wake up while in the process of climax but it is not the thoughts and the dreams that cause the climax and orgasm. While still asleep and on into the waking experience of this, mostly during the waking and waking into waking parts I can feel myself "causing" *eh-hem* the experience with one of my subtle bodies.