[GTALUG] VoIP.ms Softphone -- opinion?

Hi all, Anyone using "VoIP.ms Softphone" app from Google store? Why does it have low review on Google store? I'm thinking about moving my landline number to VoIP.ms. I would need another ATA box, because my current one is locked to Teksavvy. With "VoIP.ms Softphone", I can avoid buying another ATA box, and my usage will be the same as now. The only new feature would be having SMS on "homephone".