as far as i know windows_gpt, windows_2008 and hyper_v are the exact same LUN type, its just for the purpose of having proper reporting how many windows 2008 or how many hyper-v LUNs the customers have and so on.
i prefer microsoft native over dsm, so you fixed that already, besides alua no on iscsi is correct as well. As for reservation conflicts and so on, have you guys properly set up the windows cluster? you are using a quorum i assume and you have NOT disabled Client for Microsoft Netorks on the cluster network interfaces?
Besides when using iscsi i think its recommended to go with target portal groups. Shouldnt case stale scsi reservations tho i guess.