More Info About Lightroom 5's Smart Previews

One of Lightroom 5's new features is Smart Preview, which is a 2540-pixel raw format that you can generate.  They can be edited and exported just like the full resolution photo.  I was very interested in this feature because it would allow me to edit my shots faster when I don't need the full resolution photo.  However I found out that it's not exactly what I imagined it to be.

• I found that Smart Previews aren't designed as alternative files for editing.  Rather they are only designed to allow you to work on your photos when they are offline (i.e. are disconnected from the hard drive that contains the raw files).  It appears there is no built-in function to force LR to edit the smart previews when the originals are available (one way is to eject the hard drive - but also see below).
• If you really want to use Smart Previews as alternative files, it is possible to export the Smart Preview as a DNG and add those to your catalog.  You would have to take the originals offline to force LR to use the Smart Preview, then export those as DNG, then import those new DNGs.  But see below re loss of quality.
• Although Smart Previews are called 'raw' files, they have less information than the original files (not just in terms of resolution), similar to the lossy DNG format.  Victoria Brampton (LightroomQueen.com) said that if you make extreme exposure adjustments (e.g. +5EV) to the Smart Preview you may see artifacts, although those may disappear when the originals become available.
• When a file has a Smart Preview, it will load faster in the Develop module.
• If you are working on the Smart Preview (offline) and you click on 1:1 resolution, you will see the 1:1 view at the Smart Preview's resolution, not the original photo's resolution.
• When you edit a Smart Preview, the edits sync to the original photos automatically when the original becomes available.  Lightroom will compensate for the difference in resolution (e.g. in adjustments to noise reduction).