[[It's been mentioned that Odo doesn't have a sense of taste, which is odd to think about, but how do his other senses work? He has eyes and ears, but are they actually functional, or does he sense all throughout his body? If so, has he found it hard to adjust to having solid senses while he's stuck in his Human form?]]
Okay, so I wanted to save the bulk of my answers to the last question for here, because I think I can try to have it make more sense. First, we need to keep in mind that Odo isn’t a very good shapeshifter. He spent years of his life only shifting into forms he found necessary and didn’t explore outside of that scope. As such, those skills were never truly honed until he begins to work on them after he meets his people.
With that in mind, we first meet Odo with the smooth face who can see and hear, but cannot emulate a full face, nor can he smell or taste. I believe this is roughly because Odo concentrates on the aesthetic of a humanoid more so than shifting entirely into a humanoid. We know that he at least has some awareness when he’s in his liquid form, although it’s difficult for me to imagine exactly what that perception is. Let’s focus on the senses. First, eyesight. Since that requires a brain--which he does not have, at least not a humanoid one--we can only assume that these, too, are aesthetic but function in a way similar to the humanoid brain. Odo has never displayed the ability to see behind him when he’s in his humanoid form, so we can assume that however it is that Changelings see in their liquid form, is concentrated in the areas that function as his eyes. They are aesthetic, but--for Odo--they also function.
The same goes for his ears. This awareness is focused in the places of the ears that he is mimicking. The ears aren’t quite structured in the same way because there isn’t a brain present for them to connect to.
So, why not smell and taste? To me, I think it’s because these two senses weren’t required for Odo’s survival when he was being experimented on in the lab. Through Dr. Pol’s prodding and electrocuting, Odo was forced to perceive his surroundings visually and audibly. To see where he needed to go, and to hear what Dr. Pol was saying. Things like taste and smell wouldn’t have been necessary to test to see if Odo could take the shape of a cube. Since Odo doesn’t need to eat, food--and the smell of food--wouldn’t have held an interest for him. So, even if Dr. Pol had placed in some chicken or something in the petri dish with Odo, he wouldn’t have expressed interest in it, which would have eventually steered Dr. Pol away from further testing foods on Odo in an effort to be efficient with time.
Simply put, seeing and hearing were required for Odo’s survival, and so they were developed quickly. Smelling and tasting were not, and thus were two sensory modules that Odo has never given the proper time to develop.
That is not to say that he couldn’t eventually develop these structures to see, hear, taste, and smell as a humanoid would. In, “Children of Time,” we see that Odo has obviously made large steps forward in his ability to mimic a face. He even admits that he has gotten better at shifting. Given enough time, I think that Odo could properly create the structures needed to not only make a functioning sensory system, but a brain as well. After all, the Founders were able to pass tricorder and medical tests. They wouldn’t have been able to do so if they didn’t have seemingly functioning anatomy and organs--including the brain.
PHEW. To answer your last question, I believe that taste and smell would have been extremely jarring for him. In a sense, he’s a child in that regard, experiencing these senses for the first time. Except he’s basically thrust right into it. In some cases, I think adapting to the senses would have been difficult for him, particularly that of taste. But I think he also would have enjoyed--eventually--examining all he could with those two senses in particular.
