We moved to a mix of NAS and Cloud a few years ago. We wouldn't go back.
No more time spent on our servers. No more worrying about patches, upgrades, hardware failure, etc. No staff time lost to systems maintenace, backups.
We use the cloud for most project storage. Always [sic] available, at the office, at home, at client sites. Added benefits include systems backups, syncing folders, etc. Requires some trust in the vendor maintaining system integrity, but the risk is lower than at-office implementation.
We use two NAS devices for corporate data and archival storage. Each has a mirror set; I just like two devices as well because (a) they are dirt cheap, and (b) it gives me some level of redundancy in case one of the boxes goes and dies. They sync to each other. We periodically burn DVDs for offisite backup, multiple copies. This is the only weak point; maybe at some point in the future I'll add a third, off-site, sync'ed system.
In all, it works well. IMHO, it provides more than a single onsite server would provide, at a lower cost.