I went through the same rotary during my three year stint living off LaGrange St. in Chestnut Hill. Never had a problem negotiating traffic as long as I was assertive and signalled my intentions. Entering was actually easier than exiting; I usually waited for an 'escort' to get into the rotary but you had to signal very clearly when you were exiting so cars entering would yield.

As for the chain thing; I change my chains pretty often to avoid having them wear out my chainrings and cassettes. The only time I had one break was offroad riding during a particularly hard shift.