endor00: do you use p2pool?

Q.

When "block found on mainchain" msg appears, does that imply that YOU found a block? Or the pool?

Also, how does submitting shares work? I'm assuming it's easier to find a share on p2 than to mine a block solo?

"block found" is shown when anyone in p2pool finds a block. When you find a share (which is easier than solo mining a block), it's sent to all your connected p2pool nodes and they propagate it further to everyone in p2pool.

<sech1> ""block found" is shown when..." <- Thanks