Synology has been pretty prominent lately and I have run across a couple of them used by customers. I too am not a fan of NAS' and am much more an advocate for dedicated file servers. My biggest problem with them is that when they fail they fail in spectacular fashion. And because they usually use some proprietary RAID or OS it is not as simple as logging into your storage manager and seeing whats wrong also any troubleshooting is more difficult. Random drops in speed are an issue with a lot of NAS' too.
If you know all that going into it and you have good backups then you are on the right track with your thinking and research. They have come a long way in recent years. I wouldn't use one for anything except storing files that I don't care if I lose. Being able to host VM's and SSD cache are nice features.