I bought my first a couple years ago and had to have another, awesome, the best.
I'm not sure how this would have sounded if I hadn't opted for the break in. I have experienced drastic improvements in other speakers as they break in, however, and wanted to start using the amp in question right away.
The first gig I used the amp for was a delight. The sound and response from the amp was wonderful. Exactly the sound I was looking for--especially compared to the stock speaker I had in my Fender Vibro Champ Reverb. It went from a decent amp, to a perfect amp.
Got the M10C for my Marshall Class 5, fits perfectly, sounds excellent.
It's hard to rate the break-in service because I don't know how would the speaker sound otherwise, but I can tell it sounds good out of the box.
Nothing was wrong with the OEM 12-65 ROLA but I have always wanted to try this 12LA Jupiter .. I was very impressed with the build quality .. I had this bunt in .. sounds fantastic very articulate upper mods and tight bottom .. highly recommend Jupiter .. very responsive customer service as well ! 5 stars !