I acquired
a 124G a few years back during a moment of GAS and think it's really cool. I don't use it a lot, but one use it is good for is street photography -- festivals and the liike. For whatever reason, TLRs seem to be considered benign by the public at large. (Could be they don't know what it is -- or can't figure out what you're doing with it, staring down into the WLF.) The meter in mine is a pretty much non-functional, but that may be the switch that energizes the meter when the top cover is lifted. My tiny Digisix is a good substitute.
My most recent uses have been shooting infrared. It's nice to be able to compose and focus without having to remove an opaque filter from the taking lens.
I have some Rollei Bay 1 filters and can't say I've noticed a problem with their fit. One thing I have noticed, there are some relatively inexpensive Bay I filters in plastic mounts (often seen on ePrey) that are taller and also have a smaller diameter glass area than the big names. It is sufficient to see some vignetting at the corners. Also, there is a cheap plastic sunshade that goes in the inner bayonet. Both Rollei and Yashica had/have metal shades that mount on the outer bayonet, allowing the shade to be used independent of a filter (recommended).
The nasty sync trap is that if you try to use the self timer with the sync set to M (used for bulbs), the shutter will jam; the sync needs to be set to X. Some people go so far as to put tape or a drop of epoxy or silcone rubber at the sync switch lever to lock it into the X setting. (I so seldom use flash or a self timer I'm probably at risk of screwing it up.

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