I've done quite of work on Calc, and never had much of a problem. It's not a one-to-one match with Excel, but I've had few issues. I don't really use Powerpoint or Impress, save to view presentations, and haven't seen any significant issues.
I have used Writer *a lot* (I've written a novel and several proposals and projects). Once I got it used to it, I actually prefer the way I can work styles in Writer to Word, and every time I'm forced back into using Word, I find it just a huge pain in the ass. In general it doesn't molest docx files too much (unlike Google Docs which horribly mutilates styles).
I'm pretty much using LO full time at work now, and only use Word and Excel when I log on our Terminal Services server. I'm not sure I'd ever be brave enough to completely abandon Office, but I'm definitely not looking at further re-entrenching myself.