Christian Kay, in an article called “Issues for historical and regional corpora: first catch your word”, refers to “the resistance of British English writiers to using ‘-ize’ forms in words like ‘realise'” (in Archer, 2009:71).
If you are a British native speaker, or if you use British English as your linguistic model (as I do), do you resist –ize? I know I do, but can –ize be resisted, and should it? Is it a lost battle?
Anya Luscombe (see comment) has responded by saying that she thinks –ise “prettier” than –ize: so do I! For me, my reasons for preferring –ise are purely esthetic. Very odd if you think about it, or is it?
Reference: Dawn Archer (ed.) (2009), What’s in a word-list? Investigating word frequency and keyword extraction. Farnham, Surrey/Burlington, VT: Ashgate.
Bridging the Unbridgeable 
I try to resist -ize, although I admit I do sometimes write ‘organize’. Increasingly it seems British English is adopting -ize (my Oxford dictionary lists organize and realize before organise and realise and the -ize form is in larger print), but personally I think -ise often looks prettier on the page (hardly a valid argument?!).
Many words that sound as if they might be written with a ‘z’ are nevertheless written with an ‘s’, such as advise (verb) and surprise. What irritates me most is when people incorrectly write ‘to advice’ when they should write advise; the noun and the verb are clearly pronounced differently.