On this note I would like to suggest an additional complementary system of sorts, where say every member has a certain weekly quota of X 'like' credits, which will expire at the end of the week if unused (and reallocated the next again). Because of the (i) expiration and (ii) weekly quota refresh tagged to such credits, members are much less likely to hoard them. Different member tiers could possibly be allocated different amounts of like credits, if higher-ranked members are presumably believed to be 'better' judges of content, on average.
That's pretty much how merits already work for merit sources. Merits are already used as "Likes" by most users anyway, and having two systems in place to reward good posts just seems awfully redundant. It also seems like a way to circumvent the finite limitations of the merit system, which was put in place to prevent abuse.
I do see where you're coming from though. Merit rewards are spotty and could be a detriment to spammers (in which case it works) and regular users (collateral damage IMO) alike in ranking up. Theymos has expressed willingness in tweaking the system, however, so it would probably be better to simply be patient and give it a chance to work.