There are a load of door strips available that will get you around this problem. Topps Tiles sell a few, ask Gaz on here if he knows of one.
Depend on the depth of the difference in floors would usually depend on the strip you use. i used to use a flat strip with a slight edge on either side of it and it would work to join 2 level floors and floors with a difference of up to about 20mm. And i used to have a brass, silver and wood finish on the van in 3 meter lengths, then let the customer choose out of the three.
Thats the same type i use, they leave a really neat finish cause there are no screws, tip, i usually tile over the long lip on the bottom part of the thresehold bar, that way its not movin. They come supplied with self adh backing which can become unstuck in time.
Depends what your tiling upto I try and get the customer to choose their strip before I start. I like the ones that , a TT piece is screw into floor (The otherway round) then the top part is bashed in flush, no screws showing. But difficult to get back off.