I tried using Numbers across my Mac and iPad. It has some show stopping sync bugs there which result in it completely destroying documents. Then when you try and recover previous versions you get a lesson in Apple's commitment to things other than the facade on the front of their stuff: not a lot. The document versions thing sometimes doesn't even work and if it does it's so slow it's unusable. Probably backed with some low tier S3 stuff. Also the formula editor is painful at best.
TeXshop on the Mac is however rather nice.