I'm trying to wrap my head around this exciting new device. I own a iFi nano iDSD, iPhone, Sennheiser Momentum Over-Ear, Mac, and Audirvana+. Like everyone else, I'm subscribed to Tidal Hifi, which is one of the main ways I listen to music (including the very exciting ECM catalog now available). When I listen to Tidal through my Mac, then A+ is doing all of the decoding and rendering for MQA, so I don't see an inherent advantage for the nano iDSD BL. If I just have my iPhone+iDSD BL, then we currently can't use the MQA as it is not supported by the iPhone Tidal app.
The first question is whether we could reasonably expect that MQA *will* become available on the iPhone Tidal app in the relatively near future. In this case, this new iDSD BL would be one of the few truly portable MQA solutions. I'm not sure if I understand the difference between decoding and rendering in this case.
Otherwise, I guess it comes down to how much better this new nano iDSD is better than the previous generation. The two gain stages should help with more sensitive headphones like the Momentums. The built-in camera kit removes some extraneous cords. But it loses SPIDF and RCA outs.
Are there any other differences that I'm missing?
I am dipping my toe into all of this also, and others have commented, so this is dangerous territory as a noob. However, since I'm a noob, and this is a ridiculously complicated topic (it seems not just for me and you, but for people that have been around here A LONG time) I'll share what I've found, and where there are differences to what I've found, others' replies, and your impression.
I'm trying to wrap my head around this exciting new device. When I listen to Tidal through my Mac, then A+ is doing all of the decoding and rendering for MQA, so I don't see an inherent advantage for the nano iDSD BL.
I don't think A+ is getting you all the way there. It may (or may not) be unpacking back to the master depending on the master, and I do not think it renders. Also, it seems that whomever controls MQA won't let the full "unpacking" past 24/96 take place (if it's needed) unless there's an MQA certified device in the chain. The best (so far) visual depictions I've seen for how MQA works are
https://www.audiostream.com/content/mqa-decoding-explained and
http://audiophileheaven.blogspot.hk for the second link it's the blog from 02.09.2017 "The Digital Music Revolution" If it's accurate, then to me, it's a great visual sequence, and I FINALLY get it. Edited to Add - If you have time - click the link at the bottom of the blog to the John H. Darko article for more detail.
I think that with the BL or other MQA hardware devices you will get the full MQA experience. There are tons of words out there "decoding", "rendering", "unpacking" "unfolding".. unpacking/unfolding = decoding. Regardless of the terms, the nuggets I have taken away are software (Tidal itself and A+) will get you some of the way there when using a "Non-MQA certified" piece of hardware downstream. They'll do all of the unpacking in some cases, but not all, and neither render (I don't think). The only way to get all the way there is through MQA hardware. I don't think there are any software renderers. Some hardware does it all and could take a straight MQA file and rock it straight out through decoding + rendering (Meridian Explorer as an example) while some hardware (like our Nano BL friend) needs some software in front of it to do a piece of the lifting to get all the way there => software decoder + hardware renderer.
I'll leave the "Is MQA good" to the dumpster fires in other threads.
The first question is whether we could reasonably expect that MQA *will* become available on the iPhone Tidal app in the relatively near future. In this case, this new iDSD BL would be one of the few truly portable MQA solutions. I'm not sure if I understand the difference between decoding and rendering in this case.
I don't know, but here's to hoping! Hopefully that second link helped with the decode vs. render part. The other part is whether they'll have the app do any unpacking/decoding and to what extent (there can be multiple "folds") That seems to be (relatively being the key word) software/hardware intensive, and my guess is that they'd need to write it for a variety of devices. Apple is a pain, but it's a controlled environment with lots of adopters, so if they do it - my guess is that Apple would be first. Android-based systems have so many chipsets and operating systems to deal with, so if it were me, I'd do it last.
Also, if they release MQA through an app interface w.o unpack/decode (Tidal calls it MQA passthrough) then you'd still need a full hardware option like the Explorer or some other software option to do the decode/unpack. At least that's what I think today with what I have to work with. Too much to absorb (for me).
Are there any other differences that I'm missing?
Someone has directly mentioned sound quality (I'm assuming directly from the new hardware components all other things remaining equal). Also, the area I am particularly interested in is the new S-balanced output. One set of in-ears that I have (using the current DAC / AMP I have) sound FAR better using balanced. I've used information found here and elsewhere to speculate as to why (reduced crosstalk) and asked the forum (and iFi) if my thoughts were reasonable, and I haven't gotten a reply yet. However, iFi are putting some marketing behind it, so it must be important to them. I'll know when I listen.
My personal hope is that someday we'll get a mobile app with the software unpack/decode (for devices that can handle it) at least up to 24/96 and that this little beauty will (render) take care of the rest along with playing nicely with my in-ears with the combo IEMatch / S-Balanced. Until then, I'm anxious to check it out through my iMac.
Back to screaming at my computer and trying to get HDR to work properly on Windows....
To all that celebrate - I hope you and yours had a wonderful Thanksgiving
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. Always forget to check firmware on these digital gadgets. 
