I have the same problem with an iPad 1, you can go to speediest.net and download a speed-test app which measure your upload and down load speeds.
I found that my download speed is less than .5 megabytes(yuk) and uploads speeds in the 4 megabyte range, the download is definitely my problem.
I went to my routers settings and figured that the problem may be related to the multiple channel b,g &n setting. I haven't Had time to set the router to N only to see if that helps. Even if it does, I have to older laptops without N capability.
I'd be curious what others find