4x4x4 BLD: 14:04.64. 7:10 memorization time. I took Chris Hardwick's advice and just focused on moving as fast as I possibly could the whole time - this was the first time I tried it. I got very lucky, I think, because it was really easy to memorize (this is one of my fastest memorization times as well), and my memory was really secure. It was a little easy, but not outrageously so - 8 centers in the right place, and 2 edges in the right place; corners were maybe a little easy (2 3-cycles CP; 5 CO). There were only 2 cycles in edge permutation, so that was pretty easy as well, and the middle slice edges were clumped together, which makes it faster with an r2/commutator mixed approach like I use. It was also nice because there was just one obvious way to orient the cube, so I didn't waste any time deciding which way to go.
But even if it was kind of easy, I'm very happy that I finally cracked the 15 minute barrier!
Edit: My second attempt at going as fast as I can: 14:46.80. Again 7:10 memorization time. (I'm consistent!) Finally I'm getting respectable times at this. Still not especially good, but at least it's now respectable. Thank you so much Chris for the suggestion!