Feist's early stuff, from MAGICIAN through to RAGE OF A DEMON KING (so his first eleven books, basically) are solid but basic epic fantasy. Actually, MAGICIAN is quite revisionist for its time, with no actual bad guys, just people with different interests fighting one another. The writing's fairly basic, being fun but fairly simple.

After RAGE, Feist went through a bitter divorce and had to write to pay his alimony bills. A fair few of the later books are unrelated to the core storyline, and are dreadful. Feist also gets really, really bad at consistency later on and there are some howling continuity errors (like forgetting that one of his major characters in a previous book was married).

Overall, I'd recommend Feist to beginners or youngesters. I think more experienced fantasy fans will find less in them of interest, though MAGICIAN and the EMPIRE TRILOGY (that he co-wrote with Janny Wurts) are still interesting enough. HONOURED ENEMY is also really good, but Feist only provided the story for that and the text itself was written by William Forstchen.

As for GRRM, he has done more work on this book than first anticipated - including a 20,000-word novella that is being published separately - but the majority of it (260 of the 290 pages) was written by other people, and a lot of the work was done on it before ADWD came out. It should have come out 2 years ago, but has been delayed primarily by the artwork.