Netgear WNDR3700 Router - Using Wi-Fi Extender / Different Band With Same Network SSID?

I have basically the following setup: It's a home network, running with a Netgear WNDR3700 wireless router.

Wireless Devices on the Network:
Google Nexus One: 802.11 b/g/n
iPhone (Original): 802.11 b/g
Main Workstation Laptop: 802.11 a/b/g
"Beater/Other" Laptop: 802.11g b/g

Ethernetted devices on the network:
Logitech Revue: CAT-5e

I'm running both the 2.4 GHz and the 5.0 GHz networks over the same SSID. The goal, obviously, is to get everything over to N if possible. I've heard that wireless N has much better signal and transfer rates, is this true? Also, is running the two different frequencies with the same SSID problematic? It's kind of strange, because my Nexus One is having a difficult time staying connected to the network in my office while the main workstation laptop in the same room is getting a much better signal.

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What's interesting is that both are running on the 2.4 GHz networks, essentially both not on the wireless n network, which kind of defeats the whole purpose of things. Is it bad to run both the 2.4 and 5.0 GHz networks with the same SSID? If using a network repeater, is it bad to rebroadcast the original network with the same SSID as the source network? It seems that the 5.0 GHz network is getting "clobbered" by the 2.4 GHz network. Is it really necessary for me to broadcast using different SSIDs?