Besides the obvious, I run a Java-based encrypted chatserver called openfire on my TS-509.
I bought the Qnap to replace a monster-size IBM server, a 10-year-old 4-processor Netfinity 7000 M10 Server - originally with 34 hotplug scsi drives connected to it - (the computer cost my previous employer something like $35.000 in 1998) - but very soon connected an adaptec sata controller and 3x320 sata disks instead in a raid-0 (poor-mans-choice, would of course have preferred a same-size raid1 or raid10 solution... but am not made of money.. )
Previously using this IBM server for file storage (mostly mp3s and movies, maybe 3000-4000 photos, BitTorrent downloading, eMule downloading, the abovementioned Chatserver, printerserver, webserver, ftp-server and to run some longer-running jobs like MusicIP analysis for example or to unpack movie files directly on the server.
Had a raid-0-crash on this machine where i had connected 3x320gb sata to an adaptec 2410sa controller and lost everything.
Server was down for months while I tried to recover my data, bought a 1tb sata drive as target for my recovery attempts.
After several months finally successfully recovered >98% of all data on this crashed raid volume.
Tried to get the server up and running again with the old disks and a fresh Adaptec2410SA-adapter that I had bought in my recovery attempts.
Disk system crashed again after a few days (probably due to heat problems with raid-card, probably this was the reason for the original failure too) but i had my recovered data still on the 1tb disk so no problem.
Finally because I had gotten very tired of the space the server took up in my ** (sound-isolation box sized more than 2 cubic meters), the sound it made anyway and the power consumption / power utility bills for the server and for the extra fans in the sound isolation box, i threw the server out...
Wrung my wallet inside-and-out to get the qnap ts-509. Immediately extremely satisfied with size, sound level and power consumption.
Still not 100% happy with file-seek performance on this (running MusicBrainz or MusicIP to scan your music takes forever!) , but plan to add more physical memory to the qnap and possible add a second 1gb network cable directly from my computer to the 2nd ethernet of the qnap without a hub in between will probably boost experienced performance enormously)
Was extremely happy and suprised to find out that I could run my java-based chatserver on the Qnap.
Just tonight I finally succeeded in getting this chatserver to start automatically with each reboot, and learned a lot in the process.
Will probably manufacture some scripts to run on the qnap to keep my mp3-library in order and maybe find some other uses too.
Feel somewhat silly for hanging on to the IBM server for so long - but still quite happy about it because without it i would possibly have bought some qnap or other nas solution long before the ts-509 was released - and look how happy i am now that i put my money in the ts509 and not something smaller
Other alternatives considered was running my old (current!) pc as a nas server (probably Windows 2003 server or possibly freeNas) and buying a new pc for my self instead.
I am now quite happy with my choice and the only thing I am really missing is an old-style centronics printer port on the QNAP to connect my 12-year-old Laserjet 4L.