I do not doubt, at all, that this Blu-ray release may very well be the best 'FLCL' has looked. It's a dated show, already, and it is transfered from SD sources, upscaled, if you would. I also won't say that this is a "bad" upscale. That seems ridiculous. Rather, I think there are a few other reasons as to why this release earned the score I'm giving it, and I don't think content overload on a single disc is one of those problems, as the three audio tracks (two lossless stereo mixes and a commentary) shouldn't take up that much space compared to a single lossless 5.1 version, and the extras aren't all that lengthy.
FUNimation's 1080p AVC MPEG-4 encode in the show's natural 1.33:1 ratio has as many, if not more, distracting moments than there are ones that seem fine, and the key component is movement. Lines waver like you wouldn't believe on this release. A simple pan can turn the entire picture into a very slight strobe, with lines that can pulse, or move like an animated ocean wave, rippling through an outline, making sure it doesn't stay solid. Some moments even look like the film is seen through extreme heat, like a motorcycle's exhaust or an intense fire, creating a wobble.
But that's not all. Some random thick halos, hefty banding, obvious artifacts (including ones that make skin tones go purple), and extreme stairsteps compound the issue at random. If that weren't enough, there are some random very blurred splotches that make it seem as though some DNR was employed at some point to try to fix a few problem spots. The manga panel sequence in the first episode, as awesome as it is, has an effect similar to a moire, when it's merely a pan on a dot gradient. It's seriously bizarre.
Still, I doubt there has been a home video release of this show that looks any better. Colors can be stunning, a few flares are breathtaking, and there is a nice obvious bump in finer, smaller details. I will not lie and say this release looks amazing. It doesn't. In fact, it's really not pretty at all, but in all fairness, it never was, and it never will be. Sometimes good enough simply is as good as it will get.