Can confirm the lag OP is talking about. It's noticeable even with video playing disabled in settings, so I don't think it's a video or HD issue. I tried to replicate the lag with a fresh 0.8 build on my SSD and it's definitely there. Tried on a keyboard and a generic USB controller, too. It's also noticeable in all themes I tested (Nox, Glados and Default, though Default seems just a tiny bit more responsive) It's not like RetroFE is ignoring my input, it's like, when you press a direction at the right time, RetroFE doesn't change selections immediately, he takes around 0.6s to do so. Here's a more detailed step-by-step so you guys can try to feel it.
1 - Open a fresh, clean RetroFE build. I tried it with the 0.8 full build avaliable in the Downloads section.
2 - Aeon Nox should start.After the intro, press 'right' or 'left' one time. RetroFE should take around 0.2-0.3 seconds to answer, which is OK.
3 - Right before the transition between systems kicks in (the background fades out and in), press another direction. You should notice an increase in input response to around 0.6 seconds, like RetroFE is waiting for something before processing your request.
I tried to explain it with the best of my ability, but I can try to record a video with my phone if it's necessary.
PS: This is my first post, so I'd like to thank Hulshoff and the RetroFE community for making and maintaining one of the best frontends there is! Very customizable and easy to work with. Keep going!