Gradually over the course of the years, I guess - by the time I watched the first Plinkett review, I thought they were pretty lame, character-wise.
But the reviews added some significant perspective, I'd say - perspective I should've gained myself, but whatever. For example, I've always felt that the characters and acting were "flat", but I somehow hadn't thought of the fact that TPM doesn't have any decent main character, which is a main contributing factor while it's so... "flat".

You can see it when feeling the tiny remnant of an urge to root and cheer for the characters when they overcome the baddies - when Padme corners Gunray, when Anakin wins the podrace/spacebattle, when the Jedi kick some robot ass, etc., and you can imagine how much more involved you'd have been, had those characters had a decent characterization, arc and actual determined motivation (rather than sheer dumb luck) behind their accomplishments.

The most rewarding moment is probably when Obi-Wan pwns Maul, but up to that moment, he's pretty much just been a snarky to boring side kick with very little character, or role.
Seeing Sebulba owned is more rewarding than seeing the space ship being blown up, because Anakin actually puts some effort into that - and that part's just filler, padding and basically a fun subplot at best.