The apostrophe irks me. I think it looks archaic and affected, like you're trying to write an Elizabethan sonnet. But that's just me, maybe, for I've noticed my editors are definitely not alone: the Wendy's chain, to name just one example, has put up mass-produced signs saying "Open 'til late."
Tolkien and Lewis were both British. Maybe "till" as a stand-alone preposition is fully accepted in the U.K., but only in some dialect groups of the U.S. Calling it a "dialect" issue isn't even accurate, though--it's strictly a written convention, "till" and "'til" being pronounced exactly the same way. Which looks right to you? And where are you from? Are you willing to let 'til throw off its apostrophe, brace itself with an extra L, and become a word in its own right? Stand and fight, little preposition! Be free!
[Edit: hah! I found at least one source to back me up. Says here:
'Till' is not a clipped version of 'until': both are Standard words. 'Until' may be considered a trifle more Formal, but both occur at all levels. ’Til is a variant spelling used by those who think (incorrectly) that 'till' is a clipped form. At best it looks old-fashioned and self-conscious. Use 'till' instead.
[Edit #2: The historical linguistics backs me up even more, at least to the degree that you can ever use a word's history to dictate modern usage. Says Michael Quinion:
The most common belief is that till is a shortened form of until. You can see how this could have grown up, but the truth of the matter is that till is by far the older word, being recorded from about the year 800, while it took another 400 years for until to appear in the language (it’s a compound of till with the archaic Old Norse und, as far as, which also survives in the archaic unto).