Hi Andrew,
Since this is a Cluster-Mode forum I will list a couple of benefits of upgrading from ONTAP GX to C-Mode...
* The hardware platform support for Scale-Out customers is wider than the platforms that were supported in ONTAP GX. Customers who are using ONTAP GX have a limited choice of hardware platforms (FAS3040, FAS3050, FAS3070 and FAS6080). By choosing to upgrade to Cluster-Mode, customers can use all hardware platforms and expansion cards that are currently offered by NetApp.
* We recently announced the End Of Availability of ONTAP GX. This means that we will not be selling any new instances of ONTAP GX. All existing ONTAP GX systems will continue to be supported as per existing support contracts. Customers who are looking for Scale-Out solutions can look at the features available in ONTAP 8 Cluster-Mode. Details of the EOA can be found at http://now.netapp.com/NOW/products/cpc/cpc1004-02.shtml.