Late to the discussion, but here is my $0.02
I don’t like mixed insulins for one fundamental reason: they are an attempt to apply a one-size-fits-all solution and those simply don’t work worth a rodential fundament when dealing with diabetes.
In the diabetes community, there is a saying: YDMV (“Your Diabetes May Vary”). All it means is that every case is individual and nuanced and very very VERY few cases are a good fit for the average or “standard” guidelines. For instance: one person’s body chemistry and physiological response may mean that insulin A is very effective for them but insulin B is less so, whereas the next person’s reactions may be exactly the opposite.
It also means that each person’s sensitivity to different insulins is personal and individual, and that is the crux of why I don’t have much use for mixed insulins. Mixed insulins represent an attempt to use a fixed ratio of basal to fast acting insulin, and by definition also require them to be administered at the same time.
Now suppose your particular blood sugar behavior responds best to taking a basal insulin once a day, and fast acting insulin with each meal (a very common pattern, by the way). With a mix, you can’t do that. So you’re going to get less-than-optimal results no matter how hard you try.
And suppose the fast acting insulin in the mix is working perfectly but the basal amount is insufficient for you. Once again, you’re stuck. The only way to get more basal is to increase the dosage, which means you’re now getting too much fast acting insulin and must either eat more or risk hypoglycemia. Etc. etc. etc.
As you’ll discover, really good diabetes control is entirely doable, but it requires flexibility and an individually-tailored regimen. That’s awfully difficult to do with a preset mix.
End of editorial.