...so now all high-end MF backs have microlenses...
Actually, almost no MF backs have microlenses these days. The last microlensed MF backs were the P30+, H4D31 and H4D40, and a couple of Sinars (eSprit65, eVolution86H).
All the Phase One backs > 31MP, the Hasselblad backs > 40MP, and all the Leaf backs (of any size) lack microlenses. For Phase and Leaf, that's every one of their "high-end" backs, including the IQ and Credo series, as well as all of the higher-megapixel P+ and Aptus ones.
Since about 2009, there's been an interesting DALSA 48MP, 6 micron, 48x36mm sensor (FTF-6080C) which does have microlenses, and impressively low (for MFD)
readout noise of 12 e-. I know I tend to kick DALSA MF sensors a lot - they deserve it for being so far behind Kodak in dark noise, q.e., IR sensitivity, and (to a much lesser extent) readout noise - but this one actually looks pretty good for visible light! Apart from it still suffering the DALSA Achilles' heel of high dark noise limiting long exposures, it is closely analagous to the Kodak 50MP, 6 micron, 49x36mm sensor in the H4D-50/CFV-50, but with the addition of microlenses and slightly more DR. The microlenses take its q.e. higher than the Kodak 50MP sensor...but still way short of the q.e. of the equivalent microlensed 6 micron Kodak sensor (the 40MP in the Pentax 645D and H4D40).
But strangely, only one MFD manufacturer is using this chip, and that's in a tethered-only, multishot back (Sinar eVolution 86H) - no LCD, no card, no battery! It's very surprising that those who are currently 100% wedded to DALSA (Phase & Leaf) don't use it in a normal portable back. Anyway, that's yet another tangent to this thread...