I can't wait to see a good ePub output from Nisus as most technical publishing is going that way - what I see on the market is mostly bad, almost all have great difficulty in handling the images right.
I use AnyBizSoft PDF Converter which converts any PDF to editable Word, ePub, or other format. If you print your document to PDF it should be able to convert it to ePub. They offer a 5 page trial.