At nexenta we believe that storage will move to an open architecture. Using zfs as a software platform and then add commodity disks and servers as needed. Not being locked in with one vendor for growth. For most of the storage in a box solutions, if you need to add capacity, you have to go back...
You may want to post problems you see on either stackexchange in area 51 or on our forums at nexentastor.org.
I have looked for your problem, and i believe this is an open bug #8618. It is marked as High Priority and we hope for a fix soon.
On the HA, at nexenta we give you 2 choices for HA, either get a precertified kit or you can buy some PS to have it installed and certified. In addition, we do require gold support contract
It is important to remember that the l2 and zil are per pool. So if you plan on having a raidz2 and a raid 10 you will need to factor in ssd for each pool