By popular request (a couple people asked), below are my updated query stats. It's been a dynamic process to date, with a mad rush during the first wave and a slow, parceled response to the second.
Of course, that was to be expected. For my first wave, I chose agents that I'd communicated with - favorably - when I queried my first manuscript, who accepted emailed queries and responded quickly. The hit rate was a bit of a surprise (40%!). For the second wave, I sent out several snail mail queries, to some agents I was not familiar with, and to some smaller, boutique agencies who likely don't have a full-time support staff of assistants.
Queries Sent: 20
Full MS Requests: 5
Partial MS Requests: 2
The interest has been high, and I've received excellent feedback and suggestions from a couple of agents. So, I shall keep you all updated.