an application that works well for aggregating and reading forum posts
Don't think there is an will never be.
TapaTalk works, but only because forum owners modify the forum system (VB in the case of MacRumors, don't know if TapaTalk works with PhpBB or IPB), hence the support is real low.
Even if they boast on supporting a lot of forums, go figure, of all the forums I visit on a regular basis, only MacRumors works with TT.
Now, regardless of the platform, the problem is always going to be in that, even if there are basically three major players (VB, PhpBB, IPB), forums are always on different versions, with different features (not that we ask for anything fancy, I know; simple reading, quoting, replying and posting, and maybe PMs is enough) and most of all, with lots of tweaks, on different versions (even customized tweaks as well).
So it makes it hard to make an application that can do the basic thing one would do in order to make a forum reader that wouldn't require installation at the forum system level: parse HTML.