Performance gain is most likely even negative if you use it for transferring bigger amounts of data (file uploads or downloads) - since the stream multiplexing

Performance gain is most likely even negative if you use it for transferring bigger amounts of data (file uploads or downloads) - since the stream multiplexing layer will often lead to an additional copy for each sent/received byte. But that's probably not what the majority of HTTP is used for. On the other hand it will really help all the pages that are making dozens of concurrent small requests, which can't be handled in parallel through HTTP/1 due to connection limitations.