What is the advantage of a meterless "M"? Zippo, nada, nothing.
- Working meterless? You're kidding. Not using the meter on a M5, M6, M7, ZI will give you the same result. It is your choice, not the camera's.
- Working without battery? Ever complained that all M's up to M7 are FILM dependent? You have to change a film every 36 exposures. A battery every now and then. Taking - let's say - 5 sets of batteries with you on a day trip will not exceed size and weight of a single roll of film.
- Saving money? How? The price difference between a 30 year old used M4 to a 20 year old used M6 or a 1 year old ZI or a BRAND NEW Bessa is about the same you have to pay for a good external or add-on meter.
No doubt, M2, M3, M4.. are fine cameras that will deliver - in the hands of an experienced photograph - extraordinary results. But a M5, M6, M7 claims the same attributes.
A reasonable upgrade for a R2 would be a M6. Nobody has to chasten oneself....