Is text speak (e.g., RU, CU, <3 (love), <4 (really love), TTFN) an efficient use of language or is it language abuse?

The site cyber definitions claims it is useful for brevity and message tone, and I think I'm starting to agree.

I think these terms and icons are becoming necessary to assure our audience that we're not annoyed with them. It's also easier to type CU than "see you" when you're dodging the crowds on the high street. So, from an academic perspective, is text speak good or bad?