I kind of gave up on ATI about a year and a half ago, although I do have an ATI All-In-Wonder Radeon. People on this forum who have various ATI cards have reported all kinds of nice improvements starting with MMC 7.7. I have not yet upgraded past MMC 7.5, but based on what I've read, the enhancements are significant. People are reporting being able to do full frame DVD captures, which was something that you simply could not do without dropping frames on older versions of MMC. Be very careful in upgrading, but I think you will be pleased if you do it.
http://www.pcphotovideo.com has some instructions on upgrading ATI software and I suggest you follow them. People who do not uninstall the old drivers and simply upgrade on top of them often have problems. I upgraded from 7.0 to 7.5 using these instructions and had no problems at all.