What kind of internet connection do you have?
Every once and a while, iDisk does seem to crawl a bit and slow down the Finder.
What version of OS X are you using?
Even on my 450 MHz G3, I usually get decent speeds out of iDisk. I backup about 30 MB to my iDisk every night, and it usually goes pretty fast, but sometimes it's slow. I think it's probably mainly a problem with lag in the connection either on your end or Apple's. And yes, net lag, when it comes to iDisk, will usually make the Finder crawl. Same thing happens when you use FTP in the Finder.
The only thing I can really suggest, is to first download Cocktail (available on versiontracker.com) and see if that helps anything. It's just a maintence utility. The next thing I'd suggest is that the next time you use iDisk or Homepage, don't try and do too much at once. I've noticed that if I upload single files by themselves instead of multiple files, I get better speeds.
And remember, if you're on cable or DSL, chances are you've got an upload cap. Comcast caps my uploads at 30k, so it won't go any faster than that. Then take into account the fact that the iDisk servers probably get a lot of action, so that'll slow down things more.
If I can think of anything else to help you out there, I'll let you know.
enoch