And the one takeaway from these years of experience (and wasted money) is to buy the very best mount you can afford. To that I will now add the caveat: that you can afford and can carry.
To cut a long story short: the EM-11 is very smooth mechanically, is not sensitive to balance so far as I can tell, the polar scope is perfectly aligned, and it can turn out 10-minute guided subs like clockwork. I can tell from the guiding graphs that it is not as smooth as the Mach1, and it definitely has much less capacity, but I can't carry the Mach1 and tripod with one hand.
The EM-11 has an amazingly low periodic error of about 7" peak-to-peak, which is quite an achievement given the small diameter of its worm wheel (Takahashi only guarantees 20" peak-to-peak). Of course this isn't so amazing compared to the 3" peak-to-peak (< 1" with PEM) of my Mach1 - but the EM-11 is in the same capacity class as the Celestron AVX or Vixen GP, which normally have around 30" peak-to-peak periodic error.
This periodic error is of the same level as my Astro-Physics 600E QMD, but the EM-11 does not have periodic error correction. However, the EM-11 has lots of ball bearings, which means its declination guiding behavior is good. Again - not as good as the Mach1, but good enough that I don't lose subs. Which is more than I could say for the AP600 (or the CGEM, but that goes without saying).
To repeat: this particular EM-11 performs better than my old AP600E QMD, albeit with a much lower payload.
I'm using the EM-11 with an old Gitzo G1340 Mark 2 Systematics tripod, which is rated for 20 lb. Strictly speaking, the tripod is overloaded with the EM-11, about 10 lb of counterweight, and the William-Optics Lomo 80mm APO triplet, but the system is still stable. Much more stable than the Star Adventurer on the same tripod: hence as an aside, it is the Star Adventurer wedge which is the weak point of that system.
A useful fact: this particular EM-11 has the low-latitude base. It still cannot reach 1 degree latitude, but by slightly extending the two south legs of the tripod, I was able to get it down to 1 degree without need of a wedge. The additional tilt required is slight, and does not seriously compromise the stability of the tripod.
Another useful insight: the Gitzo tripod is overloaded with everything on it, but settling times are still under 2 seconds. I tried removing the rubber tips on the feet and use the spikes, but settling times actually got worse. The rubber feet act like Celestron vibration suppression pads, so should be left on.
Overall, the EM-11 meets my expectations of what a premium mount should be, i.e. it performs very well within its limits and does not require tweaking. It is not quite as refined as the Mach1, but there are no major concerns.
Note that all of my observations thus far are in using the EM-11 for imaging. When imaging, you generally point it at one or two targets a night, and hammer away with a camera. In fact, at this time, I have been using the EM-11 with its setting circles to find things (because I can't get the Temma 2 GoTo system working just yet). There's a bit of a retro feel to using the setting circles (kind of like using a film camera or manual-focus lens) but these circles work surprisingly well, so I'm happy. This is OK, because you can spend five minutes finding an object if you will be spending the next four hours imaging it.
However, as a visual mount, to show the wonders of the night sky to people, the EM-11 is a terrible choice. When I moved from the Celestron Nexstar hand controller to the Astro-Physics GTO, it was like going from the 20th century to the medieval period. The AP hand controller has a reputation for being built like a Russian tank - sturdy, but primitive. The Takahashi hand controller is like the Stone Age. There is no way to command GoTo from the hand controller.
I do have a Roving Networks Bluetooth serial adapter, and a SkyWire, so I can command GoTo's on the EM-11 using an Android or iOS device, but the mount as-is is incapable of GoTo unless you connect it to a computer or smart phone somehow.
My motivation for acquiring this mount is because the Mach1, for all its mechanical and electronic perfection, is a bit too heavy to be set up and taken down on a regular basis. I would really like to expand the scope of my observation activities and the Mach1 is simply too heavy for casual observing. I wanted a mount that weighed as little as possible, had GoTo (I have the Star Adventurer, and finding anything with that mount is a headache), and would be as nice as possible.
Of course in the lightweight mount category there is the Celestron AVX and iOptron ZEQ25, as well as the more upmarket Vixen Sphinx SXP and SX2. I did try the ZEQ25 for some time, but it proved to be extremely sensitive to balance and I never liked the strange worm tension adjustment mechanism that also served as the clutch. I could never get the tension just right.
The EM-11 is way too expensive if purchased new (70% of the price of a Mach1, with one-third the payload) but I was able to acquire this one for a significant discount off the price of a new one. It still is a rather expensive, low-payload mount, and I would not recommend it as a first (or only) mount, but for someone who already has that "perfect" mount and just wants more portability, it is a good choice.
My main concern was that no mount could ever match up to the performance of the Mach1, and I would be annoyed at the degraded user experience. Well, the EM-11 doesn't match up to the Mach1, but within its payload limits, it comes close, and the significantly lower weight is priceless.
Highly recommended! But not to beginning users. The combination of the steep price, extremely user-unfriendly hand control, and low payload make the EM-11 a good choice for second or third mount. It's the Lotus Elise of mounts, small, finely-engineered, does what it does very well, but not terribly practical.
Now if only Takahashi would bundle the EM-11 with an actual intelligent hand controller, lower the price to $3000, and include a PEC recording capability, it would be more approachable - the Mazda Miata of mounts, as it were.