So, I'm realizing the importance of extracting by weight and not volume. I'm looking at the Lunar, but I wonder if it's really useful on a HX machine; reason being that because of the cooling flush (I flush and go), it seems that I would have to either let it sit under the running water, which would trigger the timer, or I would have to have it tared out and ready to place it under the group head immediately after flushing, the motion of which I again think would likely trigger the timer, thus rendering it essentially a $220 waterproof scale without a meaningful timer.

The price alone isn't what bothers me, but since I'm guessing that, as described above, the timer would be essentially neutered, it wouldn't really provide me with any meaningful upgrade over my $20 AWS. In fact, it seems like it would make more sense to just burn through 11 of those (non-waterproof, I'm guessing the E61 will eventually kill it) over the course of a few years.

Is this logical or am I way off?

The scale and timer resets once the flow stops. You shouldn't have a problem.

You don't have to use the auto timing features. I don't on my Lunar. I flush, put in portafilter and slide on scale with cup, and simultaneously pull the lever and click the start timer on the scale.

I made this video on my DB but my routine is the same on my HX Vetrano. The extra second or two waiting after the flush is negligible on brew temp.

I use the auto timer function on my Lunar and gather insight watching both time and weight counts simultaneously noting the rate of change of weight vs time as the shot is pulled.

That's what I like about it too. I'm set up for a flow rate of about a gram out per second after 30 sec of line pressure preinfusion. A disparity of more than a few seconds short of the output in grams means channeling. As I'm cleaning and purging the steam wand during the shot, I don't have to watch it closely & can just glance at the numbers while wiping the wand.

I have an Appartamento and purchased a Lunar.

After using it for about two weeks, I found that it wasn't an appreciable improvement over my cheapy Amazon AWS scale. I returned it, and have been using the same $11 scale for almost three years. When it poops out, I'll spend another $11.

I don't time most of my shots, usually only when I switch beans and I'm dialing in my grinder. I have a separate timer that works great.

I have a Lunar and while I consider it a spendy purchase for what it is, I really do enjoy using it. I use the auto-tare auto-start function that happens when you put a cup on it. With my HX, here's how I use it:

1.) Flush
2.) Place scale on drip tray.
3.) Lock Portafilter.
4.) Place cup on scale, it auto-tares and autostarts the timer within a second or so, at which point I start my brew.

Hope this helps!