We mostly use middleman for static sites and it works really well. Recently we built a "microsite" based off of an existing full rails app we had so we went the wget route. My experiences are:

- Middleman dir structure is simpler for frontend devs to learn.

- Don't need to switch between dev and prod environments to work on the site vs. build the final version. Switching between the two was pretty painful as our rails app used jruby and was pretty large so it took a minute or so to restart the server and re-compile all the assets if in prod. Plus need to remember to `rm -rf public/assets` after switching back to dev.

- Wget doesn't run javascript so you might not get all assets. For example, we used a responsive image swapping technique like <img src=1px.gif data-desktop-url='xxx' data-mobile-url='yyy'>, which wget wouldn't know how to get those assets. So I ended up putting all such assets into a single dir and `mv`ing it into the build dir after the wget.

- Wget doesn't pull down assets inside IE conditional comments (json2.js, ie.css). Perhaps it has an option to do that though.

I've used the s3_sync plugin for middleman which makes the upload part a breeze.