I have a client who is considering doubling their NetApp footprint at one site, who wants to do quota management on around 200 users, and who thinks the built-in tools are insufficient.
I've looked at Northern Storage Suite, which seems to be NetApp's preferred solution. Feature laden, but pretty damn expensive, at $20K cost to us for the 20TB they'd have under management after this expansion.
NTP's QFS seems only to support previous generation filers.
I am going to assume you will be managing CIFS quota's. If that is the case yes NTP's QFS works well. I have experience implementing and managing quotas for CIFS users with QFS on FAS940, 960, 980. When you say previous generation filers, I will assume you are referring to 900 series.
I have not heard of an issue doing quota management on 3000 series filers, especially since we are working on rolling to 3000 currently at my new work.
If you are doing NFS quota management, it is easy with native NetApp.
I've used and deployed both of those, and I would say they are fairly equal. Northern are very responsive to the community and we've had a lot of input in to what we wanted to see from the product, so they are keen to keep users happy! NTP QFS is possibly a more mature product in relation the NetApp integration, and they probably have a larger install base.
Not sure if I have a personal preference between the 2, they are fairly evenly matched and both have their benefits. Have you applied for eval copies? Great way to test is with soft quota's. The biggest limitation always is with file ownership. A users quota has to be powered by the filer ownerships, and often "Administrator" owns a fair proportion of files. This is something you might want to look at fixing first as all software packages suffer from this limitation.
What functionality are you looking for above what NetApp native quota's offer?