The x100 with the TCL-x100 gives a 50mm (effective) focal length. I have owned the TCL for a couple of years, and it virtually 'lives' on my x100.
Some have said that it's overly large, but I actually prefer the appearance of the x100 with the TCL-x100 mounted. I should point out, though, that the TCL-x100 is large enough to block part of the lower right-hand-side of the optical finder. The view in the EVF is unaffected (obviously!).
Oddly, pictures of the combination don't (IMO) do it justice. For that reason, I suggest that you try (if you're interested) to view and handle these items for yourself, rather than relying merely upon pictures for making your judgement. HTH. 🙂