Run... run as far away as you can... and keep running...
O.K. in ALL seriousness...
I tried using Duende for 5 months, but in the end, decided it just wasn't worth it. And not because of the sound... the sound is simply amazing. Best software EQ's I've ever heard, hands down.
But, Duende is a firewire device, and it HOGS firewire bandwidth. What ever else is sharing that particular buss, whether it's an audio interface, and external drive, or even with a PCI FW card, it's performance can be jeopardized.
In my case, I already had and used several external FW drives for samples, a FW interface, An AES-16 Digital PCI card and a UAD-1 PCI card. Duende played havoc with EVERYTHING.
When Duende was the only device on my system, it worked great. But after months of trouble shooting, tech support phone calls, emails, etc... I decided I didn't need Duende THAT much. Life in my little DAW world was solid before Duende, and is solid after it as well. But with it, it was a mess.
It was my contention, as well as many others who were having identical problems, that the Duende drivers just weren't written well. Other FW devices like Liquid Mix or Powercore played nice with other devices, why wouldn't Duende? Two updates later, and it never got better.
Now, the thing is, there are some users, with FW peripherals, who are reporting no problems. So I tell folks, sure, go ahead and get it. But make sure you can return it within 15 or 30 days for a FULL refund.
If you have no problems, you will LOVE it. It's an amazing addition to a studio. But if you do have issues, just get out from under it while you can...