I have no idea about Amonkhet as it applies to Magic: The Gathering, other than the boxes and artwork got my attention in store. I don't know if the material is accurate, but it sure is useful.
This Planeshift could be used for any Egyptian-styled land or setting for D&D. I have used and written some myself, but Amonkhet has adventure built right in. It would be so easy to drop this land in anywhere. The relationship with the deites and the idea of the trials is brilliant.
Races are one of my favourite things to convert/write/steal from other sources. The races here are fantastic for such a setting but several could be used for other settings. The jackal-like khenra remind me a lot of Monte Cook's Arcana Unearthed sebeccai and could easily be used for such. The aven can be used as standard birdfolk (though are more human-like). Many people have been asking for minotaurs - well, they are here. And most interesting of all are the naga (that remind me of the 3E naga from the Rokugan Oriental Adventures). I am not sure about their 'burst' ability, but that seems to be how them move in this setting. (This race could easily be adapted with subraces, and is a solid foundation to base a snake-like race on if you don't want the limitations and supernatural forms of yuan-ti).
There are setting specific backgrounds, but these too would suit other settings. The Dissenter, in particular could be used for anyone living under a rulership they do not believe in - I am thinking perfect for my Dark Sun campaign.
And for those seeking subclasses, you get 4 ner cleric domains. You can never have too many of these right? Here are Strength, Solidarity, Ambition & Zeal. Gods from other settings that embody these ideals come quickly to mind.
James' quick conversions of monsters give a nice insight and shows how a DM could adapt any monster from good artwork. Some could do with a little more modification (such as the croc-demons not just being giant crocs - like add a feature or two from another demon), but I loved to read about new takes on old mythological monsters. The undead featuring in this setting is very cool and useful for a DM.
For a free product, I could not rate this more highly. I am favouring short, mini-settings these days and this Planeshift is perfect for a mini-setting or to mine ideas from.