A few of the things I hate about my Sony a6600

...and yet I just bought a 2nd one!

Overall, I enjoy using Sony's current top-end APS-C model for my video work and occasional photography. But there are a few things that feel boneheaded and out of place that you should be aware of:

It has some sort of AGC (Automatic Gain Control) applied to external microphones that cannot be disabled or adjusted. So you have to record external audio no matter what if you want the highest quality. (Recording internal on the camera can be convenient, but is hard to recommend on this camera.)
The SD card formatting takes a long time, because it writes over all the data on the card. It would be nice to have this as a special 'secure erase' option, but it's also annoying because (a) it takes a really long time compared to a quick erase, and (b) it makes any potential file recovery impossible—most other cameras do a quick erase that can still be recovered from using data rescue tools.
The menus are terrible. I'm not sure why... coming from years of Nikon, it just feels like I can never get a good mental map of the menus. At least I can throw the most common items in a custom menu.
Sony's 'smart hotshoe' accessories are obscenely expensive (I'd really just love a little hotshoe XLR input adapter that bypasses AGC, but the XLR-K3M is over $600).
The Record button location is awkward and requires the use of a thumbnail to press (at least for me... I don't think my hands are that big, either).

Despite these flaws, this camera takes great quality video and stills (for APS-C, at least), I don't run into overheating issues like I did on my a6000, and the larger battery both provides a lot more battery life than smaller APS-C bodies, and necessitates a deeper hand grip—which makes this camera a thousand times easier to hold, especially for photography.

The main reason I switched from Nikon to Sony mirrorless was Sony's investment in the APS-C lens lineup. I like having a compact camera body, and Nikon's answer for 'pro' use was to buy full size 'FX' lenses for their smaller 'DX' bodies, or settle for middling DX lenses that weren't that fast and were built to a lower standard.

Sony has some excellent modern APS-C lenses like the 16-55 G 2.8 that I love, and I hope they continue to invest in the APS-C lineup. Full size bodies require heavier gear (tripods, gimbals, etc.) to use, and I like to keep my setup fairly compact.