doing a quick test reveals that my linux desktop and tablet will only allow use of 3des, blowfish and arcfour ciphers.
when I copy, measuring the duration, thus:
$ time scp -c arcfour /tmp/100M user@10.0.0.180:/dev/null

I find that the speed reported drops off.

Times:
default = 2m41s
blowfish = 2m42s
3des = 5m52
arcfour = 2m44s

I couldn't get des, cast, aes128/256, or twofish128/192/256 to work.

my guess is that the default encryption means that the wifi is the limiting factor as only 3des slowed things down.

--edit-- P.S. This was to/from an Apple Airport Extreme running in a/b/g compatibility mode, bridged to a gigabit switched LAN. Times were, in case my quoted command line didn't make it clear, for copying 100MiB, so 2m41s means 621KiB/s
p.s.2. I had powersave on.