No, no, no. It drives me absolutely crazy when people rp from their phone, BlackBerry, Sidekick or whatever. Like someone else mentioned nine out of ten times they get distracted and take a lot longer to reply. The last time I rp'd with someone on a sidekick they took forty minutes to reply to me. That happened twice in and row. After that I was done.
You can't have the same quality and attention to rp you would on a computer in my opinion. Plus the character limit is annoying.