Actually, topaz isn't *quite* as slow on the Kindle 2. Yes, it's slow to open a book -- specially to open it in the middle, if you've already been reading it. Yes, it's slow to come out of sleep mode, if the book is open underneath.
*BUT* page turning as you read is quite snappy. I think they are pre-loading the next screenful. If you are actually reading the book (i.e. taking a little time on each page) the next page is almost immediately there. If you are paging through to find where you were, that's still slower. But the pre-loading is at least an improvement!