1) Runs as a Linux VM, so does not consume a Windows license. Nakivo can run on Windows if you are in a Windows-only shop, but if you have a mixed Windows / Linux environment, Linux can understand both NTFS and EXT4, so you can do individual file restores for both platforms.
2) Relatively low resource requirements. My Nakivo VM is backing up around 40 VMware guests, but only needs 2 vCPU and 4GB RAM.
3) Simple and intuitive web interface. I've even run it on my phone.
4) The dedupe functionality does not consume much CPU / RAM.
I can't say that Nakivo has the best dedupe I've ever seen (EMC Avamar holds that crown), but the low CPU/RAM resource consumption makes up for that.
5) The Backup Copy Job makes it easy to have an offsite backup for DR purposes.
I use this feature to provide cross-site offsite backups between two data centers.
6) The VMware replication feature is great for test labs. I've used it to rapidly deploy multiple VM's for testing, so it saves me a bunch of time.
7) Flash VM Boot makes it really quick to recover from hardware failures. I had an old VMware server die on me last year, and the dozen or so VM's on that machine were up and running on an alternate host 5 minutes later.
The individual file restore process is a bit clunky.
I'm not a big fan of the whole strategy of downloading individual files from the web interface, and then using a separate procedure to copy the files to the machine that needs the files.
In a perfect world, I would like to be able to kick off individual file restores directly on the client machine, but I realize that is not really feasible in an agentless environment.
I've been working around this by exporting the mounted backup image from the Transporter directly to the client machine, and then using the client machine to copy from the NFS or SMB export, as described at https://helpcenter.nakivo.com/display/KB/Direct+Recovery+of+Files+to+a+VM
NOTE: Apparently, in-guest file restore is on the roadmap for Q2 2018, so this might not be an issue for much longer.
If you are still using legacy in-guest backup solutions (Netbackup, Commvault, TSM, etc), look at Nakivo for backing up your VMware/Hyper-V environments.