Time's Arrow is a fun little two-parter. There's nothing heavy here - a threat to Earth, yeah, but not with any sort of immediacy. The meat is in the chemistry between Patrick Stewart and Whoopi Goldberg, and in the general silliness of the Enterprise bridge crew running amok in 19th century San Francisco.
Unlike part 1, which combined some classic Data with relatively pointless setup for the rest of the crew, this allows the rest of them to join in the fun. I can't make up my mind about Jerry Hardin's Samuel Clemens, who ends up being a little too annoying at times.
Anyway, most TNG fans will be pleased.