I came across what follows as I cleansed my computer.  The material originates with a Full Tilt Poker pro, whose name did not get recorded.  The info comes from late 2006, but I am guessing the advice remains applicable at most of the levels we currently play.  Content has been, of course, artfully re-written for clarity.

    Re-buy tournaments require an entire stylistic shift that seems to make a lot of players uncomfortable. Generally, the players who get the most perplexed or bothered by the re-buy structure are the ones who don't come prepared to take a few thin gambles during the re-buy period, or who maintain the delusion that buying in for just one or two buy-ins is the best strategy.

    While it may be possible to execute a limited buy-in strategy with some success, and buying in for as little as possible will certainly maximize your ROI, no doubt the biggest long term winners in re-buy tournaments are the ones who employ an aggressive (tight or loose) style during the re-buy period and are willing to double re-buy as many times as they bust.              

    Everyone knows that NL tournaments favor aggression, and the re-buy period amplifies the advantage aggressive players enjoy. 
     The re-buy period is good for establishing a loose-aggressive or fearless image, but the advantages carry over past the first hour. After the dust settles on the rebuy period and players can't buy any more chips, the table dynamics are much better defined: there are short and big stacks, the rocks and the maniacs have been identified, and there are players on tilt, muttering about how much they hate rebuys. You will usually have a sharper sense of how your opponents view you, too. With more information and familiarity, you are able to make better decisions.
    The flip side to this situation is the blackhole of the rebuy period, also known as Rebuy Tilt. There are different causes of this, but in every case you will take too many close gambles, calling off your chips with junk hands hoping to suckout, or making big plays without realizing your opponents have adjusted and probably have the best of it. Top pros have thrown away plenty of great stacks (in addition to cold-hard cash) while caught up in Rebuy Tilt.  Often, an average buyin (somewhere around 5-6x in the $100 rebuy on Stars and probably much higher in the lower limits) is probably a little bit higher than it needs to be. Although there are some great players, live and online, who have gone off on severe Rebuy Tilt and still show a positive expectation, it's really nothing more than a leak.
    That being said, you have to be prepared to take the risks and fire the bullets that ultimately win tournaments.
    Remember the importance of keeping your focus when times are tough in a tournament. Maintaining clarity after tough breaks is a crucial trait for any poker game. But when things are going badly in the re-buy period, it's important to remember the tournament is still just beginning. No matter how much you are over-invested or how few chips you have, re-buys were your salvation and you're still in better shape than the people who weren't willing to spend more than one buy-in and are now on their way home.

    In any non-satellite MTT, the money is heavily weighted in the top three spots. Given this information, your goal - always - should be to finish in the top three of each tourney you play. In a re-buy tournament, it's common to lose 25% of the field by the end of the re-buy period. This mass attrition rate can be viewed as being similar to a freezeout where 25% of the field did not show, but were still kind of enough to subsidize the prize pool.

    From a numbers perspective, the significant decrease in field size greatly enhances your chances of placing top three or winning the event. From a value perspective, the subsidized payouts coupled with the decreased field size give you a greater percentage of equity in the prize pool.
    In terms of play, good players can gain significant advantages in re-buy tournaments, advantages that are not available in freezeouts.
    Firstly, no matter how short you are after the re-buy period, the blinds relatively small.  Usually, you will  have enough chips where your M is not in jeopardy of falling into the red zone. This basically creates a deep stack tourney that allows you to be selective and pick your spots, whereas in a freezeout with a normal structure, failing to win any significant pots in the first hour usually means forcing a push in the second hour.
   Secondly, many players simply have difficulty switching gears to a normal tournament setting once the re-buy period has concluded. This creates many loose calls and ill-advised raises that are exploitable by good players.
    Thirdly, re-buy tourneys create vastly disproportionate stack sizes at the tables. Many times, this phenomena results in two different situations that can be preyed upon by good players: Stack Ego and Stack Envy. 
    Stack Ego occurs when a player accumulates a huge amount of chips during the re-buy period and feels duty-bound to bully the table and keep his name atop the leaderboard without dropping in position. This flawed sense of duty and expectation, coupled with the fact many of these individuals do not normally play big stack poker, make them prime candidates for you to double through.
    Stack Envy occurs when the smaller stacks tend to place excessive emphasis on the sizes of the other stacks at the table. Many times these smaller stacks will prematurely push/call pre-flop or fail to find the fold button post-flop, due to the fact they feel the need to "catch up." These tendencies make chip accumulation much easier for a good player.