I was in your shoes not too long ago and faced the same decision. Ultimately I went with open-e because their interface was easier to work with (windows guy), they supported win. 2k8 r2 clustering(not actually doing it but I wanted the option), and when I run into a problem I can get support for it.
Going back 2 years when i was evaluating our options, Fibre Channel targets under OpenFiler seemed experimental, where Open-E DSS v6 was very simple to configure and worked.
Although Open-E still don't provide no HA for FC lun's and no multipathing options our direct attached storage.
NexentaStor Community Edition should be in your product considerations also.
It's NAS/iSCSI limit of 12TB of Used Storage so you can attach more.
As a free iSCSI server it's rock solid.
We tried both... Openfiler crashed several times, and didn't really support fiber channel. DSS has multi path IO supprot on QLogix fiber HBAs, and it's rock solid and easy to use.. it was an easy choice.. :-)