OK, I failed my save and decided to get into the discussion.
Rules-lite RPGs are aimed at specific audiences, and thus have some advantages for certain groups. I see three main advantages to the rules-lite approach.
1. Character creation - In many role playing games, character creation can be a major hassle. With the advent of skills and feats in 3.xe, character creation has often become an exercise in min-maxing; each specific feat needs to be weighed against other skills and feats. In my experience, it has not been unusual for a group to spend over an hour making 3.xe characters. However, with rules-lite RPGs, character creation takes much less time.
Case in point, a few weeks ago, a few players in our group were unable to show. As a result, the DM decided to play a one shot Castles & Crusades game. We were able to make fully equiped characters in less than 20 minutes.
2. Easy for new gamers - Let's face it, some of the game systems that we use have a lot of complicated rules. Although 3.x rules might not seem that bad for us gamers that have been playing a long time, they can seem completely confusing to new gamers. A while back a player's girlfriend wanted to start gaming. At first, playing 3.5, she was completely confused by all the different skills, feats, and special rules. But, after switching to Castles & Crusades, she suddenly got it.
3. Emphasis on role-playing rather than number crunching - With the emphasis on miniatures, 3.5 has in many ways reverted back to a miniature wargame in terms of combat. Rather than focusing on heroic, fantastic combat, players are encouraged to think in terms of numbers and strategy. This is true in areas besides combat as well. With rules covering all types of situations, there is often a tendancy toward metagame thinking rather than roleplaying.
However, with that said there are some disadvantages to the rules-lite approach. Namely, the DM has to make a lot of ad-hoc rulings. That could be a problem for inexperienced DMs. Also, some players may enjoy strategic combat. over roleplaying There is nothing wrong with that, it's simply a different play style. Ultimately rules-lite RPGs are a matter of taste.
Just my 2cp