First off, kudos to Jeremy Crawford for leading this book. Using Tasha as the authorial voice of the book at first seems like another Greyhawk swipe, but then I read the intro and you can tell it isn't uninformed. They did their research. Tasha pens a foreword introducing herself to the reader that drops names faster than a Carl Sargent sourcebook. Unless there was doubt, she is indeed Natasha the Dark, Hura of Ket and the daughter of Baba Yaga. She reminisces of her days interacting with the "original" Mad Archmage Zagig Yragerne, the Company of Seven and Mordenkainen (there is an awesome illo of her playing chess with Mordy btw). These throw-away references are not useless however. Right there at the beginning and in her boxed text comments throughout the book, a new reader may very well wonder where is Ket, who else was in the Company of Seven or what is original about Zagig, etc. Fan-service doubles as trivia teasers.
What else do I like about Tasha as a brand name character in 5E? Wizards had all of D&D to choose from and they went with an alter-ego of the Witch-Queen from the Greyhawk setting. Not one of the Seven Sisters like the Simbul, or the thousands of other NPC wizards from the Forgotten Realms, not Raistlin, nor Azalin from Ravenloft (oh wait his pic is in this book). Worst case scenario Tasha becomes a famous D&D name alongside Elminster and Mordenkainen and she grows even more, best case scenario more and more people become curious about Tasha and what she represents, want more, and we edge closer to more official Greyhawk content in the future.