I sat through an LP and a half, and that half LP was awful for reasons beyond the actual game (mostly due to the LPers being so burnt out on spending two years LP FFXIII-1 that they spent about 6 episodes putting around New Buttom 003AF trying to get over the fact that they weren't getting railroaded as hard as before).
Because we all know that experiencing an RPG through an LP is the best way to form an opinon about a game
And I don't to sound like a asshole here but if you don't care about the game enough to play it then why bother to rant about it? Is a waste of time, and is not like people who enjoy XIII and its sequels don't know about the overblown criticism these games have with people talking about it everyday for 3 or 4 years already.
IMHO, it depends on the LP, the LPers, how comprehensive the LP is, and how familiar you are with the material. In the full LP I watched, it was a VLP (Video Let's Play) that I felt sufficiently covered the content of the game (even including all of the DLC) without cutting out too much grinding that occurred or speeding up things like battles and/or repetitious bullshit even when said things could've been sped up. Moreover, I am familiar enough with Squeenix's brand of grinding for bullshit rewards to know what it was that I was missing out on and it's not like FFXIII-2 reinvented the RPG wheel here either.
But beside the point, the reason why I watch LPs in the first place is because I either don't have the time or the opportunity to play these games myself. In the case of XIIIs 1 & 2 I don't own either PS360 and without going out and burning $300+[the cost of the game]+DLC dollars just to play a mediocre JRPG and a tech demo of said JRPG, LPs are the only other legal way to see what the games offer.
As for my ranting, why does the internet exist for if not to sperg and rant? Yes I rag on the FFXIII games a bit much, but what else am I supposed to do with my communication skills in regards to video gaming? Hope I just happen to know somebody who actually plays video games and isn't some kind of antisocial sperglord that only ever wants to talk about the stuff he plays while never letting the conversation last long enough to let you get in a word edgewise? Besides, I most rant for cathartic reasons, just like anybody else would.
Also that edit I made earlier wasn't just aimed at FFXIIIs 1 & 2 but also crappy fiction like Twilight and 50 Shades of Grey which are turning into multimillion dollar franchises that make me feel like I wasted my time on trying to make video games or having a meaningful career and should've become a sell out novelist who can turn dreck into dosh with a wave of his magic pen instead. (The current state of the video game industry has also played a part in my current disgust with it "Video gaming! Its not for women or any civilized/productive individual for that matter." (I may have watched the most recent VGA recently).)
Edit: Also this.