I'm inclined to agree with your points, I always preferred the linux client over the windows one, but skype just gets on my nerves recently. My team has switched to mumble for meetings and stuff and we find it immeasurably better. Plus, channels are a much better method for general collaboration than the outdated concept of conference calls.
We use the murmur server on a linode, so it's totally free (if you have a linux server already). Just "apt-get install mumble-server" on ubuntu server.
Still have to use skype for external calls and stuff, but for internal comms we love it so far.
I know it's not free, but you can easily find fully managed mumble hosting for $4 month (for up to 10 people connected at a time). It may not be completely free, but it's pretty damn close.
And mumble should get even better in a future update when it switches to Opus which combines their current CELT codec with, relevantly, Skype's SILK for better low-bitrate speech encoding.
