My experience is Alt-F has breathed new life into a box I was about to retire.. After some initial concerns - I'd recommend it. My DNS-323 is more responsive than it was before.
I have a DNS323 Rev C1 - with JBOD - I use it to stream HD to my media player (NMT) and also to download (nzbget).
I previously used ffp+optware - especially for unfsd which was more stable than Dlinks nfs offering, the latter of which kept crashing my unit. I need NFS as I stream via homeplugs, which SAMBA/CIFS doesn't see to like.
This worked OK for nearly 2 years but Lately nzbget IO started to really kill responsiveness, despite no changes to configuration or speed.
It was not due to nzbget CPU, or threads etc., I think it was something to do with the file system and IO.
Anyway, I thought I could spend hours investigating or just take the plunge, install an alternate firmware and hope the problem goes away.
I googled around and decided to flash my Rev C1 nas directly with the Alt-F RC2.
After flashing it spends a long time checking the disks, so be patient. It then mounts them as read only - so that requires a quick change in the GUI.
Data is preserved after flashing, but make sure you back up anything precious beforehand.
I did have some issues re-installing nzbget from Alt-F package management because I had backed up the existing /ffp folder but kept the original in place. I should have just renamed it, out of the way.
Also at one point I lost network access after a reboot - but I did the 20 second reset , and was up and running again.
After a bit of tweaking I find it is a great improvement over the Dlink firmware.
For nzbgetweb you need to enable the php session,xml and I think json modules for lighttpd (this can all be done via the gui)
Now both SMB and NFS seem more responsive (I didn't do any benchmarks)
Then I used the control panel to convert the file systems from ext3 to ext4.
This greatly reduced the time to delete large files.
It also has web pages for SMART monitoring with email alerts, etc.
Its a shame Alt-F ipkg is not compatible with optware as there are a lot more optware packages.
However I still grab the occasional package from optware if it doesnt have too many dependencies (eg gawk)
I think the GUI could do with a few more confirmation dialogs, as its easy to click something by accident , and off it goes...
(the visibility of the inetd service on/off button is a bit worrying - but I suspect a 20second reset will rectify if I do accidentally click on it)