Okay, here's the thing. It really bugs me when every new fantasy that comes out is compared to Harry Potter...as that is a very high standard and it sometimes just sets the book up to be disappointing.
I recently finished reading Magyk by Angie Sage, which has a quote on the paperback comparing it to Harry Potter.
I'd say that the book was "fine." There were likeable characters, an exciting (if a little easy to predict) plot about Jenna, the rightful future queen (the "Queenling") who as an infant was hidden to protect her from harm...and the takeover of the kingdom by the evil Necromancer. The book also explores the fate of Septimus Heap, the seventh son of a seventh son, thought to have died in infancy and prophecized to have extraordinary magykal powers.
There were quite a few things about the book I liked...yet I felt it could have been edited down to about 60-75 percent of its actual length without affecting the plot or characterizations.
I think fantasy fans who enjoy a lot of detail about creatures and other "magykal" things would really like this book....but I, myself, would not put it on the level of Harry Potter...whether quality plot, writing, or characterization-wise.
For those who have already read Magyk, we do have the sequel, Flyte, and the third in the series, Physik, is set to be released toward the end of May, 2007.