I have considered the Pico as well. It can be powered from a (car) battery and a battery with a charger connected to it is much more efficient than a regular power supply on a UPS. But it the end I decided to go for the latter option anyway because it is much more versatile. Now my entire network is running on the UPS, including a couple of PoE devices, without modifying their power supplies.
I too chose a 80Plus power supply, but I have recently found out that this label is rather useless because it specifies the efficiency at a rather high load. While at a more realistic load the efficient isn't always as good as suggested. Most computers don't consume (much) more than 60Watt in idle, while they're often equipped with power supply with a capacity of 450Watt or more, given it a load of ~11%. Power supplies meeting the 80Plus standard (
http://www.80plus.org/documents/Server_ ... 9Aug07.pdf) are still allowed a steep drop of efficiency below a load of 20%, just the area where it is used the most and where things get interesting (of course in absolute numbers the amount saved is less too). For maximum efficiency a power supply should be selected carefully: We usually pick one with a capacity big enough to assure it can handle the load, sometimes up to a factor 10. But proper capacity calculation will save more energy in the end.
The 80Plus organization publishes efficiency measurement report of every power supply with its label. You can find these reports here:
http://www.80plus.org/manu/psu/psu_join.aspx
Interestingly they stop measuring below a relative load of 20%. So for a computer using 60Watt of power in idle, a 5x60Watt=300Watt power supply would be ideal. If the load is spread across the rails equally and your computer doesnt contain high-end graphic cards etc