Thanks for all the quick suggestions; this obviously will be a useful forum. To respond:
To help with dropped calls:
Turn off MAC address Spoofing, which may cause problems because of conflict between modem or router and Ooma device...
Is this on by default? I temporarily hooked up to the Telo and made a quick tour through its management pages yesterday, but don't recall this setting. Also, I'm unclear why such a conflict wouldn't cause a consistent problem, not the occasional dropped call I've had.
The echo problem:
Turning off MAC address spoofing may help, but probably won't. See if there is echo when using the Ooma Telo handset. Many times echo is not present when using the Ooma Telo handset, but will be when using your other phones.
Unfortunately, the echo occurred with a Telo Handset, and has happened on two successive calls to the same number (from Minneapolis to a Yuba City, CA landline/cordless) a week apart. This hasn't happened on any other calls (including with our Uniden cordless and hardwired phones), so I'm not sure Ooma is the culprit. I'm going to have the other party try a different, hardwired phone next time.
...You can buy two network cable splitters, put one at each end of the network cable going from the media closet to the wall jack feeding your Telo, and add a couple of short patch cables at each end. This will allow you to use the single CAT5 cable running between your media closet & wall jack as if it were two separate ethernet cables.
I was aware that 10/100 uses only two of my four pairs, and thought about splitting them, but didn't realize there was a plug 'n play solution—thanks. (BTW, I have several 5-port switches of various brands and vintages—one of which is a gigabit model. It seems to work fine, so I assume it's just wasting its gigabit capability and auto-negotiates down to the 10/100 of the rest of my system—as do my three Macs.)
I guess my only reservation about splitting that run is that I'll be introducing an extra 150 feet of Cat 5 between modem and router (which are physically side-by-side and close-coupled now), with possible attendant QoS issues. However, the solution is cheap and easily undone, so I'll give it a try. OTOH, several people have reported no problems with a downstream Telo, and I hadn't thought about the possibility of managing QoS in my router (a Belkin N1 Vision); I'll have to look into that.
However, the responses I've seen so far suggest that neither of the only problems I've had (echoing and dropped calls) are QoS problems that could be solved by moving the Telo ahead of the router. (Does anyone have a contrary view?) I have yet to see any classic QoS problems such as stuttering and lag, so maybe I actually fall into the "works fine downstream" camp and am chasing a solution in search of a problem.
For that matter though, I'm becoming less averse to moving the Telo to my wiring closet; is there any routine (e.g. voicemail) stuff I can do from its panel that I can't do from a Telo Handset? (I have two.) I once thought the Telo was a speakerphone, but it's just a speaker, and the only thing I think I'd lose is the ability to monitor a call without picking up a handset.