Sometimes I love texts. "What are you doing next week?" is a good one. Lets you check your diary and get back to me. I rarely have my phone glued to me so replies can take a couple of days for me. They are useful for passing information - eg "I'm going to be in York on the 19th of August: train museum then shopping. Want to come?" That's a great text. Date and place and enough time to call/text back to say that you want to come. Or just turn up on the day, if I text an invite I don't care if you don't reply.
Texts are also great for mothers: you can deal with them when you have time, not when the phone rings. When
DH is out of range I can text him and he'll get it quickly. I'm more likely to pick up a text message than a mobile phone answerphone message so appreciate texts for that.
I don't reply to a "happy birthday" but usually do to a "merry Christmas".
I hate text conversations: just call. It's easier.