In principle, functional languages promise straightforward architecture-independent parallelism, because of their high level descrip- tion of parallelism, dynamic management of parallelism and deterministic semantics. However, these language features come at the expense of a so- phisticated compiler and/or runtime-system. The problem we address is whether such an elaborate system can deliver acceptable performance on a variety of parallel architectures. In particular we report performance measurements for the GUM runtime-system on eight parallel architec- tures, including massively parallel, distributed-memory, shared-memory and workstation networks.