Amazon has been touting Silk's cloud-accelerated browsing as one of the standout features of the new Kindle Fire, but we weren't blown away by its performance. HTML5 development tools creator Sencha agrees, showing in a recent test that it may actually be slower in some cases. In a head-to-head against a Fire with the feature disabled, the accelerated browser often lost, and while the test can't be considered comprehensive, it certainly doesn't reflect the sort of stunning improvement Amazon suggested. Silk's HTML5 performance also underwhelmed: the tablet scored 95 out of a perfect 100 in the Acid3 test, which measures a browser's compliance with current web standards, and provided choppy CSS animation performance overall. While it's still early days for Silk, it looks like Amazon may have some work to do to live up to its own hype.