A dumb question about ERC-4337: how many people are running bundlers today? how many user operations have been successfully bundled on mainnet so far? 

perhaps @tim or @0xstark.eth have some ideas here

Technowatermelon. Elder Millenial. Building Farcaster. 

nf.td/varun

Last analysis I did over a stretch of a few hundred blocks, I saw somewhere around 5-7% of txs landed on chain but were not found in the mempool (most would be due to private bundles sent to block builders). This number may give a bit of intuition to your question.