Like I said, I have never used or edited a smashwords document, so I can't comment on their quality...
When you edit/review your smashwords, are you displaying it in a "text only" type view, or can you see the html formatting codes "behind the scenes"?
I would submit again, as gmw did above and ePub/eBook creators would all agree, that you may not "see" the errors if it is a "text only" type view. But those errors are still there. Whether or not those errors are noticeable on a users device/app are dependent on several factors....make/model/version of device/app to name a few (sometimes it feels that which day of the week it happens to be is a big factor
). Each has their own little quirks, and what looks fine on a nook might look like total dog doodoo on a kindle or iBooks.
Originally Posted by gmw
They don't show up in print, but they can upset the xhtml export ... When you open a typical Smashwords epub it's like walking into a house after a wind-storm has been through, and any minor adjustment you might want to make for your own purposes is more difficult because it's all so messy...
When you use automatic conversion processes you are taking a big gamble on the quality of your product.
Having said all of that...you are completely welcome to do whatever you wish..."I have no dog in this fight!"....I was simply clarifying what Jon meant when he recommended using a "hand crafted" book.
 For clarification - I am NOT an author - but I did stay at a Holiday Inn last night!
I do not participate in the creation of the story...I am simply speaking from my experience as an HTML coder / ePub creator....and longtime READER (for many decades)!! I have personally seen absolutely atrocious eBooks (formatting not content) from "professional" publishers. When I look at the html coding to try and find out WHY these books are in such sorry shape, they invariably show the signs of having been through an "automatic converter".