Well, the tech guys here have worked on the current interface so it shows everything in this box as you'd see it in the post. So, no need for a preview. However, if this isn't working then there's a need to sort it out so it does. We won't see a return to the preview we had on the old system but I do want to make sure this one works properly.
When you say "all over the place" what sort of content makes it go like this?
It's normally when adding something external into a post. YouTube, occasionally pics, the odd quote. Especially when trying to do multiples of something. I'll press submit only to find spaces I deliberately entered between items have gone, sometimes paragraphs have disappeared leaving just one block of text. On occasion items put in have been missing completely.. It just seems somewhat erratic sometimes as to whether it'll be submitted exactly as you see it, and the more complicated the post, the more likely it is that it won't be.
Don't get me wrong, it's only every now and again though. Possibly I'm just fussier than the software allows for. 
"I was suprised at how young you look, and you're much better looking than yoursig pic suggests.... But, yes, you're right, you are socially inadequate." ~ Ceri "You've not met Ben, have you? When you do, all will become clear..." ~ Nik Samson "You are the Osama bin Laden of fashion." ~ Splat "Weirdo" ~ Billie "Hairy Ben's always right. Never understimate his omnipotence." ~ londongal76