Jones Day London

Have various offers from MC and US firms, one of which is JD. These positions are for TCs, not laterals.

I'm interested in whether (i) is the culture that good (what are the horror stories), (ii) what are the opportunities like leaving the firm (is it respected enough to land at K&E 5PQE), (iii) is mid-market good for career progression (are there any downsides)?

Any advice would be great, especially personal anecdotes.