I canāt speak for the buttons on the RS but yeah, my RM ones wore out and needed replacing on my earliest machine. I did it myself. Bit of a faf disassembling but once done the repair was easy.
Sound wise itās deffo dated sounding. Youāve got plenty of useable sounds including plenty of drum kits but donāt expect DN quality! Re effects. I donāt know where Yamaha pillaged the fx unit from but, again, itās got a dated 90ās vibe going on. The midi effect is the midi delay which basically triggers extra notes, either internally or over midi. Obv. The other fx only work on the internal sound engine.
Iāve used the odd patch from the internal sound generator in newer tracks Iāve made so not totally unusable. I used to love to stick on a pair of headphones, plonk the RM on my lap and sketch out a tune using the internal engine, then once firmed up subbing the internal sounds for midi synths. It sat at the heart of my set up before I got a DAW (renoise) and even then I used it for recording midi patterns which I then recorded into the DAW. I found it much faster than recording midi into the DAW directly. Plus I was still using the RM to write the song, DAW was used as a multitrack recorder with arrangement done on the RM
Donāt be surprised if the knobs start falling off, theyāre very loose fitting on the pot shafts. Touch wood Iāve not had any screen issues with any of my RMās. From memory the latest firmware was only available as a ROM upgrade but donāt quote me on that. Iāve never upgraded mine.