The special is all right, but it is quite obviously animated in Flash, which I found distracting at times. The voice acting is pretty good, but Rob Paulsen is just too high pitched for Mr. Whiskers. Reading the books, I always imagined him with a much deeper voice. Scott McNeil using his Chief Thunder Hooves voice would have been a better match, in my opinion, but ah well. But there is just one major thing about it that bugs me, and that is the expanded role of Cyrus Grape. In the book, Mr. Grape only shows up at the beginning and end of the book, claiming ownership of a skating pond and forbidding anyone to use it. Mr. Whiskers disagrees with this, but has no way to prove Mr. Grape doesn't own the pond, until, in the course of cleaning up for his sister's visit, he comes across a deed which proves the pond is actually on his property. In the special, Mr. Whiskers and Cyrus both claim ownership of the pond, which leads to Cyrus examining his deed and finding no mention of the pond. Which in turn leads to him sneaking around outside Mr. Whisker's house and talking to the camera a lot, plus sabotaging Mr. Whisker's house cleaning to the tune of a "You're a Mean One, Mr. Grinch"-like song (Barry Manilow is no Thurl Ravenscroft, but the song is kind of catchy), all to keep Mr. Whiskers from finding his deed.
I should mention that there is precedent for this expansion. Cranberry Christmas is the fourth book in the series, and the second appearance of Cyrus Grape. While in this book, he's mostly just a curmudgeon, in his first appearance (Cranberry Halloween) and later appearances, he doesn't hesitate to try something shady. So it makes sense to use him being up to no good as a way to expand the book into a 24-minute television special. Knowing this, I still find it annoying. Probably because all the Cyrus sneaking around stuff means that Mr. Whiskers freaking out about Maggie and her grandmother cleaning out his house is pretty much eliminated, and that actually would have been pretty funny to hear in Rob Paulsen's voice.