Finally announced for the PC and PS3 platforms, Rockstar will release their big DLC packages The Lost and the Damned and The Ballad of Gay Tony on March 30th. The extra content has been available for nearly a year on XBox Live, but is now trickling down to less-favored platforms.
The packages had wide critical acclaim, but I think I may have moved on from GTAIV. The technical issues and DRM that hampered the title on the PC really got in the way of my enjoyment. It was certainly a good game that I had a lot of fun with when it worked, but it was hard to get past the graphical bugs and continual disk read errors. At $40, unless the games are bug-free, I wouldn't consider subjecting myself to that frustration again.