Yeah, delay on both phones in this abode. A couple friends have noticed it as well with other VoLTE phones. I assume it is early tech bugs, as expected, that will get flushed out sooner rather than later.
Dont get too hopeful on that. SIP is not rocket science, but there are just some limitations to its implementation that cannot be gotten around too easily. After thinking about this issue a bit, and applying what I know of SIP and how it integrates, it seems to me if there was any sort of an easy fix they'd have done it before releasing it. But, they needed to keep pace with AT&T, so they pushed it out the door. My hunch, is the codec negotiation between the client and the server is taking a bit longer than they hoped, which is going to need some decent code re-work to fix. It could also mean either a codec change entirely, or updates to both clients and servers. The changes made to the protocol for use over VoLTE is minimal, but obviously Verizon could have proprietary code involved which could either speed up or slow down the bug fixing process.
Bottom line, VoLTE from anyone is far from ready for prime time any way, and in truth it benefits the carriers a hell of a lot more than it benefits us. Verizon has the most robust, scalable and proven voice technology available in the world (Sorry, CDMA 1xRTT vs ANYTHING GSM has is far superior for density, propagation and use of spectrum) and the widest deployment in the US.
That said, its still fun to play with.