Glad you’ve enjoyed them!
Let me answer your question in two sections.
First, the pros and cons – the pros are, most obviously, that the Lannisters were able to quickly defeat their most serious opponent in the War of the Five Kings at a time when their own manpower (as opposed to that of House Tyrell) was starting to get tapped out. And in the process, the Riverlands and the North fall into their column (to an extent), which gives the Lannisters a geographically united realm they can govern. The cons are that the Lannisters are now universally seen as bad actors – which, as we saw with the second siege of Riverrun, makes it much more difficult to engage in political relations.
Second, the long-term picture. This is where I think the odds start to look worse for House Lannister, because they’ve become more hated than they are feared, which Machiavelli warned against. While the Young Wolf is dead and Edmure is in chains, and the North and the Riverlands are temporarily pacified, both provinces are on the verge of a new revolt that the Lannisters do not have the resources to deal with, and new leaders are going to take over from the previous set.