iirc ipodlounge liked the airplay. smaller and easier to use cause the built in display, and they found it to be a more powerful transmitter. if i were getting a transmitter id probably get the airplay. only things i have against it are that it doesnt use the dock (line out) and is ipod only, but those arent that big a deal.
[edit: checked out the ipodlounge forums and found vastly varying reports w/the airplay. dont know if theres a batch of bad ones or just differing opinions or what. so uh, if you buy it get it from a place thats easy with returns i guess.]
as for ftp, i barely use it, my needs are super basic. so with that in mind, heres the crap ive used:
cli ftp - well it works as long as you know the basic commands. i use it when im too lazy to open an app (although the amount of typing is probably more work).
golive - sorta ghetto, slow, but its worked for simple syncing and uploading to my site.
fetch - uh, havent used it in a while. screwed up some transfers for me before so i ditched it.
fireftp - firefox extension, turns the browser window into a 2 paned ftp client basically. been using this since i was told about it a while ago until...
cyberduck - never heard of it until a similar thread showed up on another forum. tried it out and it works for my basic needs so far. using the last 'final' version instead of the betas, not sure how much a difference that makes. it can integrate with subethaedit or textwrangler or whatever which is nice i guess.