The thing with the 88M is the same issue as every bus powered interface, when your battery is getting drained your dynamics go down the tube as well. Sure you can grab a cellphone charger, been there done that and you can get by but I always grab the one from 10 below instead of the brick I spent $100 on for this purpose and then we get into the whole issue of Crappy non locking USB and lightning cables. Let’s face it USB and lightning make a Dsub look like a mic cable made of Kimber Silver and Rhodium XLRS.
While I have used a battery for small short light duty sessions (under 2 hrs) with expected results, again it's important to maintain perspective of the design utilisation intent.
I have a powered hub I use with the 88M and it's never fluctuated or drop in performance as long as I am not expecting the box to be anything other than what it is.
If I'm honest, I too had very dim hopes for what a bus powered box could actually provide. Happily I was proven wrong with the 88M.
I had mine since it was initially released and still have not had a single performance or driver related issue with it.
Mine was recalled by Neve shortly after I bought it but it was the most professional experience I have ever had from a pro audio company. I wasn't even aware there was an issue, they contacted me, sorted customs and shipping and got my box back to me in around 10 days all up and it's never missed a beat since.
The 88M is actually a peerless,stand out performer that is right in line with the quality or product and sound one would expect from AMS Neve.
I find interfaces as a whole the most loathsome and purchasing them the most embittering process one can tackle in pro audio. The world of interfaces is full of liars, cheats and hacks to a point I no longer trust any of them to just be straight about what their products can actually do.
Neve never soapboxed the 88M, they stated it's intent and who it was targeted at and then rolled it out to stand or fall on it's own merit. That fact alone is worth mentioning. That it sounds so damned good and works so well, the box has earned it's place deserving the overwhelming praise it has received.
No box is perfect and not every system is going to get along with even the most consistent performing of interfaces.
No software no faffing about with over stuffed options just bog it down, it's almost too simple and too easy to use.
Whatever the box lacks when compared to AIO boxes is not missed in my world.
The often mentioned headroom differences between the 88R or 8801 compared to the 88M is just engineering gibberish in my mind, of course they are going to be and perform different and if someone buys it without understanding how the 88M can serve them regardless of those difference than I'm not entirely sure that the word engineering should be anywhere near their job description or occupational title lol.
The 88M sound is very very much in the same sonic terrain as it's namesake suggests.
Professional users will know and understand how and why to manage it's power needs.
It's just not a big deal at all in my opinion.
I think a 4 channel version would be amazing so long as it didn't then require software but I think Neve are planning a completely new line of their digital cards that will make expanding the 88M a breeze.
Give it a try and see how you go, I'd love to know your thoughts after using one for awhile!