I'm excited because while B2 + Cloudflare is great, the speed+latency isn't the greatest for some applications. So there's definitely a place for R2 here to compete more with AWS S3 than B2.
I'm a fan of B2 as well, but for some use-cases they seriously need to up their game. They only have three datacenters (CA, AZ, and Amsterdam), they still don't have a public status page, their admin UI is lacking lots of features (like proper invoices and different 2FA options), their permission system is very basic and inflexible, and they are not integrating compute with storage like AWS already does and Cloudflare will eventually be able to. However they are impossible to beat on cost, and for me their latency has recently improved significantly and has become much more stable, so I'm not going to move anytime soon.
Latency (time to first byte) in serving infrequently accessed images was a big problem with me and B2. The cost was low enough that I've stuck with it though and coded on the front end of the site to use placeholder images until the real media can be retrieved.