I give them a B+. Not because of overall record, but because of the hurdles and obstacles they overcame.
Reason being is if you look back at the starting line-up at the beginning of the year, you had Bonafacio, Lake, Barney, Castro, Rizzo, Schierholtz, Olt, Castillo, and Shark. 2/3rds of that starting line-up has been changed, and they still improved greatly from that team.
Granted, their were struggles with the rookies (some expected), but the bullpen in the latter part of the year was very solid, and Hendricks and Wada filled voids where Wood and E-Jax struggled.
The Cubs traded away most of the opening day starting line-up as mentioned above, and also noted is that they lost their #2 starter at the time (Hammel), and by far their best left handed reliever (Russell) too.
To overcome all of that, to also play without Rizzo and Castro for a good while the last month or so, and to hold their own and also beat teams like the Orioles, Cardinals, and Brewers. who were all in the playoff race at the time is a major accomplishment.
To me, it shows this team is headed in the right direction, and with a few roster moves, this could make 2015 very interesting to say the least.
Here's to hoping this happens.