Overpriced..
I tried the DXi virtual appliance, worked well, but the asking price made me choke - In the end I got 2 Dell DR4100's with 8TB in each, for the rather nice price of £8,000 for both!
Its a shame, as it was a good product that would have worked well in the low-cost SME sector, instead they tried to compete with the likes of Data Domain and Dells DR4100 which offer hardware based de-duplication, which Quantum simply don't have the reputation/brand to allow.