For the test I used the CAT5 cable that came with the unit and connected it directly to my workstation (Intel GilGal), this way there shouldn't be any bottlenecks caused by hubs or other network devices.
As test I copied a random 700MB file from and to the TS-109. I used GetRght to measure FTP and HTTP performance. To test Samba performance ATTO was used. HTTP can't be used for upload, therefore there is no score for it.
HTTP seems to be the slowest solution for big files, however HTTP isn't meant for large file transfers.
FTP shows reasonable speed, even though I believe it could be improved by tweaking TCP/IP settings a bit.
As you can see the performance in ATTO shows the same speeds as most Gbit networks. Far from Gigabit speeds, however a noticeable improvement over Fast Ethernet. Since Samba is most likely the main way to access the NAS I'm happy that this is also the fastest.