Having just invested in a momentus XT hybrid drive such as the ones that this marvell controller may "stop dead in their tracks" according to the author, I think I can say that it probably will not. I put the seagate drive in my 2 year old Core 2 Duo laptop and the difference in performance is considerable.
As a result the Momentus Hybrid drive has the laptop market all on its own which is something that the Marvell controller cannot serve because most notebooks have a single slot for a drive and even if they had two, their connectors are in such a way that adding the Marvell controller will not be possible.
On the desktop space things are a bit different but again the simplicity of having a single drive rather than a controller, an SSD and an HDD will probably appeal to most users.
The last reason is probably cost. A 500Gb Momentus XT hybrid drive retails for around 120 to 150 dollars. To get the Marvell working you are looking at around 60 to 70 dollars for the drive, 20 to 30 dollars for an equivalent SSD plus the cost of the Marvell controller itself so it looks like they will cost more or less the same and have the same performance.
Judging by the all the above and the head start that the Seagate drive has, I think the Momentus is probably going to be the more prevalent of the two.