This is often my struggle. Wait till a new version is available or not. I am eager to by the new NAS as I have some time in the next weeks to set it up. But I know I will have some regrets if the 509 has an upgrade in a month or so. Can anyone tell me when the 2xx and 4xx where upgraded?
I beta test for QNAP but I have yet to hear anything concerning Q1 releases. This doesn't mean a great deal b/c they don't use me for every round. Also, I would not broadcast future release information in order to maintain my standing with QNAP as a reliable beta tester. The question of waiting for new models is always on the table - I'd like to hold out for ZFS support but... well... it could be a while. If I had to buy today I would get the 439. There is little difference between the 439, 509, and 639 series aside from the drive capacity (4, 5, 6 bays). They are all based on the Intel 1.6GHz Processor with 1GB RAM, and 128MB flash memory. It appears that only the 509 is seated in a socket making processor upgrades possible.
There was a round of upgrades Q1/2 and Q4 last year. The x19 and x39 series came out upgrading all lines except the 5xx series. They also released the 410 at the end of Q4 which was an upgrade to the 409. I believe there will be another upgrade in late Q1 or Q2 2010 but I would not expect it to be more than a single unit upgrade like the 410 was to the 409. If I had to guess they will upgrade the 509 and / or perhaps the 809 series given that the other series were upgraded last year (2xx, 4xx, 6xx). Also worth noting is that QNAP will likely try to consolidate some of these products in a future round of upgrades. Consider that they have three units in the 4xx space - 410, 419, and 439. I expect the next upgrade will consolidate this line to one 4xx series unit.
Next, I see the logic in the full linux distro. This would also solve a small issue that I have when using the media server Swisscenter. This server uses the zip function which is not supported on the QNAP (and my Synology 407 has the same problem)
I toyed with building a NAS from scratch. The learning curve would not have been significant but didn't feel that I had the time, and I wanted something that was supported (as time goes by this looks more and more attractive - lower costs, easy upgrades, full control, and more knowledge on my part). I went with QNAP because it is the most extensible product in this space. That said, these units would be so much more robust under a full distro. For example, their are some security concerns which I could easily address if I had access under the hood - IP tables for starters. I'd like to run a proxy server for content filtering but can't make it work because I don't have access to the tools I need. And on and on. Still, I do like the boxes that I have. They do suit my needs for the most part and I run those other services under a dedicated linux box.