I use it. It's very convenient to have a second person plural pronoun. It also flows well with other abbreviations, such as "d'y'all" (do y'all), "y'all've" (y'all have), "y'all'll" (y'all will), and so on. On occasion, I might say "you guys", but mainly when talking with foreigners who might not know what "y'all" means. I also refrain from using it when writing formal prose such as letters to companies, because it's technically improper. "you all" should be "all of you" 