For pitching, I'm going to break it down into more easily-digestible bunches. For this version, I'm going to look at the Cubs in 2012 and then the people most likely to make the team (for Opening Day) in 2013.
Jeff Samardzija is the de facto ace of this staff. All 5 of Fangraphs' projections has him sliding in FIP, and I might agree with them. When the FANS projection slates you for 3.72 coming off of 3.66 and 3.55 (albeit 2011 was in relief), something is a little wonky. He's been getting lit up in the Spring, but he says he's just working stuff out (he actually said he threw a belt-high fastball down the center of a plate so a dude could hit a home run off him, so he could work with empty bases (or something like that). He's a good bet to be a solid #2 rotation guy.
Travis Wood is scary. He looked bad last year and he was actually really lucky by FIP-standards. He doesn't have a great fastball and he doesn't change speeds well: his FB last year sat at 89.4, his changeup at 79.6. He's a pitch-to-contact guy who had an obscenely low .244 BABIP last year – unless some part of his kit has drastically improved he is going to get rocked this season. A team with 2012-vintage Wood getting 20 starts is a team that loses over 90 games. In an ideal world, he'd be a LOOGY (wOBA of .279 against lefties).
Chris Volstad was a total disaster last year. He struck out less than 5 people per 9 innings. You can do that if you are an incredible pitch-to-contact type that induces groundballs: Volstad is not that guy. His LD% has steadily risen over the past 5 years. According to Pitch f/x, he didn't have a single league-average pitch last year.
Paul Maholm started the year of really poorly but became a solid starter for most of the year. The Cubs traded him for Arodys Vizcaino, and that move will probably work out for both teams (a definite win-win for both sides at the time of the trade – Maholm had another year of cost-control).
Matt Garza could have possibly netted a Top 50 prospect at one point, if not more. At this point, the best the Cubs could probably hope for is a Christian Villanueva-type. He might sign a team-friendly extension, or a prove-it deal with the Cubs, but if the injuries didn't make him a vastly inferior pitcher, he's still a large injury risk for whatever team ends up with him. It sucks, but that's the truth.
Ryan Dempster had an incredible run with the Cubs last year. Shenanigans with the trades aside, he ended his tenure with the Cubs as a generally good player. He wasn't very good for the Rangers after the trade, and he's not going to like it in Boston either.
Justin Germano has played parts of 7 SEASONS despite sporting a career ERA of 5.27. He is the very definition of a replacement-level pitcher and played like one for the Cubs. That might be a little harsh given his freakish strand rate and .339 BABIP, but at some point you have to realize that you are giving 12 starts to a 30-year old non-prospect with no future in your organization and move on. The Cubs have.
Chris Rusin is not very good. He was another guy who just had an awful strand rate last year (64.7%) which points to either an inability to pitch from the stretch or variance. We'll probably see which it is, unfortunately, because the Cubs don't have many backup options before they get to Chris "I can give you 5" Rusin.
Edwin Jackson is this year's big FA acquisition. He's probably going to give you 190 innings of slightly-above-average pitching, which is just fine by me. He's a #3 on an average team, which means he's probably our second-best pitcher depending on how you feel about Garza, and his contract and age will still be fine when the Cubs are a good team again. He did lose a mile from his fastball last year, but he lost a mile from all of his other pitches too, so I'm not incredibly worried that he's suddenly incredibly hittable. It'll be very interesting to see if he can keep down his LD% like he did last year.
Carlos Villanueva isn't very good. He was hit-lucky and strand-lucky last year, and those worked in concert to mask a year that wasn't as rosey as it looked. He's an ideal 5th-starter/swingman type, and he'll likely occupy that role with Chicago this year.
Scott Feldman was the anti-Villanueva last year. He FIPed 3.81, but had an ERA of 5.09. He left only 61.0% on base, and his BABIP went from .239 the year before to a fairly-high .318. If he repeats his peripherals from last year, he'll be just fine, and he's got the stuff to work as a 4th of 5th starter on an average team.
Scott Baker is a huge injury concern. If he comes back at the level he used to pitch at, he could be a great steal for the Cubs. However, he signed with the Cubs, so he'll probably spend half the year on the DL, and the other half doing his best Chris Volstad impression.
All in all, the Cubs will at least have more depth than last year. That was a serious, serious problem last year (on the order of 5-10 wins lost to sub-replacement pitching), so we've improved pretty drastically in this area. However, we are still basically average at this point.