What I find funny about the word "tis"...
is that if you are writing it in a chat box online or in an e-mail and you really meant to write "it's," either way you're okay.
I'll give you an example:
Oh I can't wait to see you tomorrow! Tis splendid our schedules worked out!
Oh I can't wait to see you tomorrow! Its splendid our schedules worked out!
I mean, really, you're only missing an apostrophe in the second case and that's not too shabby.
Words are so awesome.