Am currently using FreeRapid on W7 as i was unable to download jDownloader. however there is a small bit of lag with freerapid as well, but maybe due to slower processor(celeron m 530 - 1.73Ghz) in my laptop.
Try DownloadHelper, a Firefox add-on. Supports Rapidshare premium, queues, and you can directly open files from within the manager. Only thing lacking is a download speed limit setting.