I have never played D&D. I've played Rifts, Palladium Fantasy, Heavy Gear, and have GM'd Rifts
It's really hard getting into Rifts. Someone above said that Palladium has made Rifts into one giant cluster fvck and he's kind of right. I feel Ultimate Rifts did resolve some problems, but only from the original rules. There's still the problem with escalation, as all of the original character classes are inferior to the expansion classes. And then there are dragons in the original book, which is simply overpowered in a lot of ways. Palladium has a problem of adding more power to its newest classes. When I GM'd I restricted players to only HUMAN classes from the Ultimate Rifts book, and that worked out very well. I ran a killer campaign too, everyone wanted to keep playing but I got bogged down with school. I have more free time now but I don't know where the character sheets even are =p