Before considering VoIP.ms as the provider, first look into how close their servers are to your particular locale. This probably isn't a big deal, but some people do care about it.

They have access servers in Montreal, Toronto, New York, Houston, Dallas, Los Angeles, and London (UK). If any of those are "internet close" to you (extremely likely), then there's unlikely to be an issue with it. They say their main servers are the Dallas and Houston ones.

Ping times can be an indication, but a traceroute will really tell the story. Eg.
Code:
traceroute to sip.ca2.voip.ms (24.102.60.67), 30 hops max, 40 byte packets
 1  zippy.localnet (10.0.0.2)  0.328 ms (my local firewall)
 2  lo-100.erx05.tor.packetflow.ca (206.248.154.105)  54.735 ms
 3  2120.ae0.bdr02.tor.packetflow.ca (69.196.136.66)  54.803 ms
 4  gw-mountaincable.torontointernetxchange.net (198.32.245.17)  58.049 ms
 5  colo4500-to-core-main.bgp.mountaincable.net (24.102.5.13)  60.621 ms
 6  cn45-core.mountaincable.net (24.102.5.18)  61.529 ms
 7  ca2.servnet.ca (24.102.60.67)  66.465 ms

Note that our DSL line is "interleaved", which means those times are 35ms longer than they would be on a regular "fast mode" DSL line.

-ml