We are testing the Synology DS211j within our gigabit network which is pretty much as good as you will get for a home or small office environment. It is a mixed network with several 1GBit switches for ultimate performance.
Performance is quite good, averaging 84 MB/s read and 44 MB/s write across our network to a 1TB RAID 0 configuration.
Next we created a folder of files, 500mb/s in size with a variety of data , from small database documents to larger jpgs and bmps.
Mixed transfer requests obviously cause a performance hit. We found with the small amount of onboard memory (128mb) that the DS211j was often running at the limit.