I've used Ultima Interior Guard Plus, Optimum Leather Protectant, Meguiar's #40 and 303 Aerospace Protectant on my gray pebble-finish and hard black plastic interior trim. After application as per manufacturer's instructions and the products have dried, all the products looked and felt the same way to me, no gloss or oily finish, which is how I like it.
The Ultima product does not claim any UV protection on the label (but adds it on the website, hmmmm), which concerns me. It looks/feels like clear oil and smells a little like leather. It comes with a nice foam applicator.
The Opt product looks and goes on kinda like melted butter. It has a faint chemical smell.
To me, the Ultima and Opt products are a little easier to apply because you can see where you've applied them and how much you've applied.
My 5 cent summary: The Ultima is waaay too expensive. I like the Opt & 303 products, the Opt is a little cheaper in small quantities, alot less $ in larger quantities. Megs dosen't do it for me, but that's more a personal reason then performance based.