Brief impression:

This small thing is simply amazing, compared with its predecessor ( only have ud100 for a few days before selling them)
UD110 still heats up like the UD100 but not as fast and goes as hot
UD110 is slightly more forgiving on bad recordings as compared with the UD100

As i only have the fiio E07k which utilize wolfson 8740, my impression will be compared to this unit.

UD110 has a larger sound stage compared with E07k
E07k gives a much warmer sound compared with UD110 ( which explains why UD110 has a bigger sound stage compared with fiio's)
Once again UD110 is still not as forgiving on bad recordings/source as E07k. Not sure how to explain this in detail but to keep it brief E07k gives a very musical sound where UD110 just doesnt gives that, should i say it is a very neutral sound?
Fiio's E07k definitely gave a "meatier" bass or should i say the quantity. I am not saying UD110 lost in term of bass but they give a different type of bass. A more detail bass and doesnt hit as hard and powerful as fiio's.

This is based on a 30min listening and could change when this unit burns in. I apologize in advance if there are typos, wrong usage of certain terms and grammar error lol

Sum-up
So does the UD110 come out a winner compared to UD100? On its own, yes without a doubt. But putting them together, I won’t call UD110 a significant upgrade in the sonic department. I like the fact that UD110 sounds richer and lusher over UD100 while keeping the same resolution and soundstage, but it isn’t going to be twice or thrice as good or going to ‘blow your mind’, so to speak. If you already own an UD100 and have no plan to make small step of improvement on your upgrade plan, then you can skip the UD110 without missing out too much. But if you are just looking for a tiny USB DAC with a great sound, this is the one to get.

A thank to Stoner Acoustics for the UD110 sample