A great article about BTS 2004 performance tuning has been published to MSDN.
This paper was developed by our consultant for a *big* customers using BizTalk for clinical B2B messaging.
Summary: This document describes performance tuning for low latency messaging. It explains how to achieve the lowest latency possible for a messaging-only scenario using the HTTP adapter for sending and receiving. It provides details about the software and hardware configurations. (64 printed pages)