In 2010, for the first time in a decade, the Texas Rangers won the AL West, finishing with a 90-72 record. They went on to defeat the Tampa Bay Rays in the American League Division Series, and subsequently took the AL Pennant, beating the Yankees in six games. They eventually lost the World Series to these guys, but they had still won the first pennant in franchise history.
The 2011 Rangers built on that success, as they ran away with the AL West crown, winning a franchise-record 96 games. Once more, they made it all the way to the World Series, and lost. They'll give it another shot in 2012.
Luckily for the Rangers, their only big loss this offseason was C.J. Wilson, who signed a five-year $75M contract with the Los Angeles Angels. They did well in replacing him, too, as they spent big to bring in Japanese phenom Yu Darvish, shelling out $52M for the posting fee, and handing him a six-year $60M contract (with $56M guaranteed). It's rather difficult to project Darvish's performance based on his NPB stats, but he appears to be good for three to four wins above replacement in 2012, which is fairly close to Wilson's value.
The Rangers rotation in general, which ranked third in the majors in fWAR in 2011, should be top-notch again. Derek Holland broke out in 2011, posting a 3.94 FIP across 32 starts, and even with some regression, he'll likely be worth 3+ WAR. Matt Harrison also saw a lot of success, following a move back to the rotation. His 4.2 fWAR in 2011 placed him 13th in the American League, right between the Red Sox one-two punch of Josh Beckett and Jon Lester. It looks like Alexi Ogando will be heading back to the bullpen, but the Rangers will fill the void with (former) closer Neftali Feliz. ZiPS has him projected for an ERA/FIP in the mid-3's as a starting pitcher, which would make him an above-average (3+ WAR) arm. Lastly, there's Colby Lewis, who was excellent in 2010, but merely average in 2011. With a little resurgence, he'll be yet another solid arm in that rotation.
In Darvish, Holland, Harrison, Feliz, and Lewis (this list isn't in any particular order, by the way), the Rangers have five starters who project to be above-average. Throw Scott Feldman and Alexi Ogando into the mix as rotation insurance (it looks like they'll be pitching out of relief to start the year), and the Rangers clearly have the deepest rotation in the big leagues. It's a truly remarkable mix of depth and breadth (which is to say, they have a lot of starters, and said starters are all good).
As good as their starting pitching is, their offense is even better. It's hard to believe, but the Rangers only managed a 100 wRC+ back in 2010. Following the additions of Adrian Beltre and Mike Napoli, they improved to a team wRC+ of 113 in 2011, tied with the Yankees for the second-best in the majors. Their entire projected lineup, one through nine, is made up of guys who were with the Rangers last year. In other words, they have the same really good lineup as last year. It's hard to imagine Napoli (.444 wOBA) and Beltre (.379 wOBA) repeating what they did last season, but the offense will certainly be elite in 2012, as it was in 2011. There's some upside too, like with Leonys Martin. He was disappointing in Triple-A (.297 wOBA) after tearing up Double-A (.423 wOBA), but he should get a chance to work his way up to an everyday role (presumably beginning with a Triple-A stint).
The bullpen is yet another strong point for the Rangers, who added Joe Nathan this offseason. They guaranteed him $14.5M over two years, which seems like quite the overpay -- considering Nathan has been worth exactly 0 WAR over the last two seasons. That said, he was one of the most dominant closers in baseball from 2004 to 2009. Ogando will solidify the 'pen, as will Mike Adams -- who came over via trade in July. I'm not sure if the Rangers plan on keeping Koji Uehara, but he's one of the most underrated relievers in baseball: over the past two seasons, he has 140 strikeouts and 13 unintentional walks in 109 innings.