Well let me defend my point of view more concisely. I really should have typed:
GigaBit ethernet is a bit unnecessary IMO, and not many consumer grade routers support it
The initial part of the sentence I believe is more relevant. If the OSD2 is designed to play & record content up to 1080i, then the ports on the board should be fast enough to stream the file. So doing some rough math:
1920x1080x29.97fps x Qf estimate of about 0.27 = 16.8Mbps
for video data alone. Adding in sound and container data, the stream rate should be well within the actual capability of 100Mbps ethernet. So Gigabit is unnecessary for the OSD2's core functionality.
Staying on the core functionality notion, while it will be nice to plug in your external USB hard drive into the OSD2 and have it shared on your network, that's not what it is for. It's not optimized for transferring files from USB2 to ethernet, and the 300Mhz CPU may be the bigger bottleneck.
One thing I think the OSD2 does need is 802.11n support, because that will future-proof it much more so. (I consider it akin to the USB1.1 port on the OSD1 - its greatest hardware weakness)
But you are right in that Gigabit ethernet is the way forward, especially considering High Definition video files that we'll need to deal with. However such products are still more expensive than the 100Mbps routers in my local PC store, and consumers mostly prefer faster wireless IMO.
 This is based on rough estimate from OSD1's MP4 algorithm, where 1 hour of 640x480 content at 2000kbps = 1GB, implying a Qf
of roughly 0.27. I imagine the OSD2 will have a better compression algorithm so this value will be lower, but this is worst case.