The hooplah?
It provides more bandwidth at the cost of increased latency compared to 100Mbit NICs. Typical home broadband connections won't benefit as they're usually limited to 10Mbit (Well, here in Australia, the cables are limited to 10Mbit max).
If you have alot of users OR if you move gigabytes of files on a regular basis, then yes, its worth the investment...Otherwise...Don't waste your time.
Regarding NIC brands, I only go for 3Com/Intel/Marvell. Why? They offer zero CPU usage under load. (in addition to being well supported for a wide variety of OSs).
Whereas cheapo ones like Realtek and VIA ones bring similar performance at the cost of higher CPU usage. (And bring a few headaches occasionally).
In addition, you're actually shifting the bottleneck of performance around...By getting gigabit, you've removed the network performance bottleneck, but shift it to the PCI bus. If you have a mobo that has a separate PCI bus (say 64bit slots), then its not an issue...But if its a typical desktop mobo, you'll see it hit a ceiling.
Typical PCI bus is 133MB/s (in theory, in reality its about 120MB/s or so).
Gigabit ethernet is 125MB/s (in theory)...But we'll say 80% of that to make a conservative estimate to account for latency due to protocol and physical wiring = 100MB/s.
Depending on the chipset, this leaves very little bandwidth left for other devices on the PCI bus. You can see why Intel and Nvidia chipsets now have a dedicated gigabit ethernet connection separate from PCI bus.
There's a few things to consider.