First: Top post, new-red.
Second: One of the interesting things about the Alonso versus Lucas (as a defender) argument, is that it reflects on the improvement in Lucas's game in the last year. A year ago, Alonso was legitimately a better defender. Not that Lucas was necessarily poor - he just got nervous, went into too many challenges he didn't need to (which is why he as the unnecessary fouls reputation).
In the last season, played through necessity, Lucas has improved. He's calmer. He trusts himself more. So do his team mates.
His weaknesses are the same. His long range passing game isn't great. But then again, he's going to playing in a midfield with 2 of Aquilani, Gerrard and Mascherano. All three of those have good to great long range passing games. (Mascherano's being much better than his short range game). On the flip-side, his short range game - particularly in the final third - is reemerging after disappearing following his move from Gremio. The pass for Benayoun has been replicated frequently in the last few months - it is no longer a fluke. That, plus the increasing number of pass and move players we've started integrating into the team will help him (though, as a side effect of helping Liverpool).
He's a squad player who was asked to be first team this season. But as a squad player, he's a really decent one. Ask yourself: Jenas or Lucas? Denilson or Lucas? Mikel or Lucas? Gibson or Lucas? He's not necessarily better than all of those (my glass aren't that red tinted). But he's not worse either.
And he's improving dramatically. The Lucas on today shits all over the Lucas of August '09, nevermind the Lucas of August '08. That's a good thing.