Not a fan of the trend towards TPBs, I must say. They're more difficult to hold, rarely actually contain more content, and used bookstores often don't accept them.
In the old days, though, we often got three hardcovers per year. Now there's a similar number of TPB novels instead, plus the collections of short stories/novella - and they're cheaper than hardcovers. Pocket seems to have phased out the first-release-in-hardcover strategy for the time being.
A few years ago, people were asking if Pocket would be switching their ST MMPB line to the new larger MMPB size, but so far that doesn't seem to be on the cards. (I was very annoyed recently when the new "Indiana Jones" novelization was available only as a hardcover or the new larger-size MMPB. It's the first time the switch has really affected me. And the new book doesn't match my first three.)