The refresh rate and lack of color are definitely downsides to e-ink displays, but the upsides (imho) outweigh them when for an e-reader.
They barely use any power (it really stinks when your book runs out of batteries), and perhaps more importantly, no eye strain!
Honestly, I find Amazon's Kindle lineup to be a little weird. Unless I'm mistaken, the Touch (which isn't the most expensive model) has the most advanced software, which means it has access to features the other Kindles do not (include the Fire). The one that immediately comes to mind is the x-ray feature. Really bummed out they didn't backport this to older Kindles, or at least include it with the newer models like the Kindle Fire...