Is it true that everything smells and tastes better when you quit smoking? Nope. Everything smells and tastes more accurate when you quit smoking. More accurate does not necessarily mean better. When your first spring time rolls around after you quit smoking you will likely smell the aromas of flowers that smell much more intense and also likely much more pleasant than you perceived while you were still smoking. You will likely say that these aromas do smell much better.
But drive by a garbage dump or a sewage treatment plant now and see how much better it smells since you quit smoking. The odds are it will not smell better but may in fact smell much worse and more pungent than before.
The same principle applies to tastes. You may find that you start to perceive new flavors in foods. You may find that certain vegetables in a salad actually have a flavor while for the years you smoked you may have thought they were only added to give the salad a crunch. This does not automatically mean you will like the flavor.
You may find that you were spicing foods a lot more when you were a smoker too just so you could taste them. If you prepare the foods with the same amount of spicing as you did while smoking you may find that it is way over spiced for your new found taste buds.
So while not everything is going to smell and taste better--things are going to smell and taste more accurate. While not all things will smell better, one thing you should know for sure is that you are going to smell a whole lot better to the rest of the non-smoking world as long as you always remember to never take another puff!