Their API is pretty straightforward to use; the Nuget package .Net package lets you send SMS messages with a few lines of code. The cost per SMS message seems to be the most cost-effective. Review collected by and hosted on G2.com.
It can be tricky to track down message failures, occasionally, messages show having been delivered, but customers are adamant that they are not receiving them. Some markets can have issues with deliverability, including the US, where we have had to use an alternative solution, but from outside of the US the cost per SMS message is probably the cheapest solution. Review collected by and hosted on G2.com.
