Right now, I'm just using asset_id (https://github.com/moocode/asset_id) to dump my assets on S3/CloudFront with md5s in the filenames, pretending to myself that that will make everything fast.
It seems like all the gems provide different things, whether it's CSS minification, JS minification, includes to combine many files together, automatic aggregation of multiple JS/CSS files, CSS sprites, easy uploading to CDNs, different strategies for cache busting (md5 of file vs node timestamp)...
I'm presuming that with Rails 3.1, everyone is going to switch over to Sprockets 2.0 from Jammit (which is what it seemed like everyone used before). However, I honestly have no idea what's going on or where the big wins are.
What's up?
http://ryanbigg.com/guides/asset_pipeline.html
DHH also talked a lot about it in his keynote this year at RailsConf:
http://www.rubyinside.com/dhh-keynote-streaming-live-from-ra...
It _does_ work, but I am quite looking forward to the integration of rails 3.1 to get rid of it.
For a look back in time, see the Hacker News thread for Sprockets 1.0, from two and a half years ago: http://news.ycombinator.com/item?id=487601
Some alternatives include the very popular Jammit from DocumentCloud (http://documentcloud.github.com/jammit/), Alex MacCaw's Ruby port of Stitch (https://github.com/maccman/stitch-rb), and Mislav Marohnić's "poor man's Sprockets" (https://twitter.com/#!/mislav/status/87899513649496065).