I use the internet download manager version 5. I never really needed one until I got a rapidshare premium account. I tried the free ones and also made trial runs of some of the pay ones. I finally settled with IDM, and it has worked perfectly, even on the largest downloads. My recommendation on whatever manager you pick is to download only 3 files max at a time. From personal expierence downloading more than 3 at a time will cause corruption of the files. With IDM I have it program to never download more than 3 at a time.
i have internet download manager also//but i download 8-10 at a time... it just depends on the file sizes,or your internet connection.
Orbit Download Manager for me =] it even speeds up the downloads. on normal downloads i use with firefox i usually got 140-150kb/s but with orbit i usually get 160-180