The four consecutive group head temperatures of the particular machine at the top of this thread is shown in the shipping page above. Their measurement appears to be part of the final QC protocol for each machine. This is one is obviously very stable.

In my experience it depends on the style of shot you're pulling; turbo shots don't require as much boiler pressure to fully soak while trad shots with finer grinds sometimes need some help once the boiler pressure gets towards the low end. It's easy enough to add a little pressure though, especially in direct mode, and with the bleed valves you can 'mini-fellini' to get full piston displacement once the puck is soaked. I found that the variable boiler pressure was mostly an issue for the first day or two when I was pulling a ton of shots back to back (driving the group head hotter) and getting familiar with the machine (so didn't have much of a mental model).

Ok, more time to play with the Argos today. The more I have used it, the more I like it. Someone mentioned that it appeared to be some condensation inside the boiler cap pressure gauge in one of my pics. I hadn't noticed it but without even asking, Ross contacted me and said a replacement boiler cap was in the mail. Now that's what you call excellent customer support!
I love how quickly the machine is ready from initial startup. Less than 10 minutes. By the time I have cleaned the portafilter and ground beans for the next shot, it's ready to go. Not sure how much time is actually needed between shots but it's less time than I need. I only make espresso, no milk-based drinks, so I can't speak to the steaming performance but it seems powerful when I tested it.
On a side note, I completely forgot that the base machine DOES have Bluetooth built in! I didn't buy the transducer so I wasn't thinking of it but I saw a video of Ross using his phone app with a transducer-less machine and so I downloaded the app..... sure enough the app easily connected with the machine and provided instant feedback. Amazing! Attached are pics from just before first shot and the other pic is after 4 consecutive shots, 27 minutes later. I increased the brew set temp after the fourth shot which is why that reading is different.
Shots are coming out extremely well. I have noticed that the machine likes a very fine grind....even finer than my La Pavoni. I am going back and forth between a Kinu M47 Classic hand grinder and a Ditting Kr-1203 with SSP burrs. Both are resulting in very tasty and beautiful shots from a variety of coffee I have roasted myself and store-bought.
Summary after a few days of use: I love it! So consistent and easy to work with. It's a beautiful machine on the countertop and a small footprint.