Yeppers! I'm still happy with it even though now Corel is its home. (But Corel is Canadian, and Canadians are nice, no? :))
I always have that (the correct invalidly nest html) checked. In fact, when I imported my Livejournal, LJ had a TON of errors in their LJ-generated html. I coulda done better when I was manually typing all of my html in notepad back in the early 90s. I had to go through and make insignificant changes just to have wordpress fix lj's problems. And there are still some really ugly bits of html left in posts I imported from lj.
So far, I've been very happy w/ cutting & pasting from WordPerfect, though I do go through the post after and check it each time, and have occasionally had to make tweaks in the html editor. It's usually odd spacing issues. I also code the html text formatting tags (em, strong, etc.) separately, either using wordpress's visual editor or putting in the tags manually in WordPerfect (and I've not had a problem with that, either).
Basically, checking the post as your creating it (in preview as well as html) and then proofreading it again after it's posted can avoid most problems w/ cutting & pasting from other sources, and other sorts of problems, too -- measure twice, cut once! :)