I rolled out about 30 Sangoma S500s before moving on to Yealink T46S/G, which is what I sell now exclusively (in addition to paid EPM). My problems with Sangoma phones:
- Sketchy firmware - Last one I tried a few weeks ago made the handset volume way too loud, had to roll it back
- Failure rate is worse than Yealink
- Slow interface
- In past firmwares G722 codec created high send volumes, so I only deploy G711 on these devices.
Send Volumes - Could never get a sidecar to work properly
With all that said, they are reliable enough for day to day, but not worth the cost of free phone apps and EPM. While visual voicemail is nice, my clients don’t seem to care. Most have voicemail to email which bridges the gap.