While I liked it, I'm not too upset over Sonic X no longer being on TV, since it's on DVD as well (though it'll be sad that television will once again be Sonic-less, possibly for a very long period of time)...
But what I WILL be sad about with this loss is the farewell of Kirby, since I know these episodes may never be released on DVD. Only the first 12 episodes and the last 5 episodes are out, and while it's nice that 4Kids has recently been releasing new volumes of the series, these new volumes only come out once every six months with only four episodes on each. Thus, we'll likely only get two or three more volumes before 4Kids permanently loses the license, leaving nearly 3/4ths of the series never to be seen again.
Though, what upsets me the most is that this is the loss of a block we all came to know, love, and loathe. It gave us great shows such as TMNT 2K3 and Viva Pinata, revived Sonic X and Ultimate Muscle from their Japanese cancellations, showed us just how wrong dubs can go with One Piece and Mew Mew Power, but still managed to give us good dubs with Shaman King and Kirby. It was a block that began as Fox Box, replacing Fox Kids, and marks the end of a tradition that spanned nearly two full decades...
It's a bit sad that I feel more sentimental over the loss of Fox Saturday mornings than I did over Toonami, but really...
They probably won't replace it with simply infomercials, since they still have the E/I quota they have to fill by law.
Now we just have to find out the exact date 4KidsTV will end.