Having nothing but trouble from our DD's, though it's been since found the problem may not have been quite as much w/ the devices directly, but then again we do still see occasional issues w/ ours that are resolved w/ nothing more than a reboot - we thought we'd give the Dell DR's (DR4100 in our case) a try. At a fraction of the up-front cost, a fraction of the yearly support renewals, native 10Gb, and better performance once the data gets onto the device, we will not be renewing our sky high DD support and simply letting them die on the vine as unsupported misc. archival storage. Granted, Dell has recently bought EMC so not sure how much of a moot point it would be anyway.
Our Dells came in at about 1/3 of the cost of our old EMC's and been much more stable and much faster.
Now, as far as dedupe appliances, based on my experience I wouldn't recommend on buying into the fad for any manufacturer. Before walking in the door here I had about 4-5 years' experience w/ Veeam and the old classic staging to plain old Windows storage first, then pull that off to tape for archival. It just worked, rock solid, for years. We'd keep about two weeks on disk since that's into what most of our restore requests would fall, plus of course last night's disaster recovery. We had a very open expectation w/ users if we had to go to tape, it would take longer, especially if it was off-site tape. No problem, everybody was happy.
My current company had long before since into the dedupe sensation w/ two pairs of DD620's and a pair of DD2200's (two data centers w/ matching sets, cross-replicated at the DD level) before I walked in the door. As mentioned lots of writing problems that have since turned out to be a VMware NIC driver problem, but still occasionally like to fail authentication, which fails the backups for that night - or weekend, albiet a simple reboot the next morning fixes it until the next time. We have had to remove/re-add to AD authentication when they get *really* broken a few times but it's a quick fix. Still, "reliability." Now, speed. Dedupe devices will ingest really well, and that's what the marketing pushes. Try a restore and you'll be waiting around for a very long time. Setting your jobs to largest block size (16+TB) will help, but it's nowhere near pulling directly from disk. Start a VM from backup? No, though Veeam indicates there's a better chance of it happening w/ V9. Everyone here has been appalled w/ restore speeds, and we once had an emergency restore of about 2TB of our main file server. Took a couple of days. File level restore? What used to take around 10-15 min. back in the day of just plain old disk storage now takes no less than half a work day from dedupe. Maybe more if it bombs out half way through, the user says no that's not the file, etc. I've since been able to tune and tweak to get it better, but it's still dismal. And here we're writing straight to dedupe which is not best practice. I've tried pushing getting some staging disk space to help mitigate emergency restores but no, there's still the expectation that dedupe devices are perfect. In the end, they are effectively a one-way street of data storage. They'll store great, just don't expect to get much back out of it, at least not any time soon.
I get the dedupe/compression aspect - about 86%-88% real-world (despite what the sales manager tells you). That's fantastic, we're storing hundreds of TB's in just around 30-40TB of raw dedupe storage. I completely get the attraction. Veeam's dedupe and compression may not quite hit those marks but v9 has really slugged the crap out of it, I've seen our v9 final vbk's and vib's shrink to 1/3-1/4 of their previous v8 size in some cases due to dirty blocks being written to storage in previous versions. However, what is the cost of a large JBOD vs. even a Dell DR, or especially EMC DD? I bet a big tray crammed full of disks and v9's much better storage capabilities would win way out over a dedupe box - and you can actually restore files/VM's, run a VM from backup(!!!), more easily manage, etc. I would recommend staging JBOD w/ v9, and final archival to tape. Walk away from the cool aid of dedupe devices. They're marketed quite well but just don't deliver back to you when you need it back out of them. You asked for recommendation, these are my opinions based on experience.