... or, the bane of my existence! I finally finished this a couple of months ago for my cousin's college graduation gift. It was almost 2 years in the making!
Obligatory, pseudo in-use fashion shot!

The whole shebang, on our queen-sized bed:

Close-up of the squares:

Aaaand the backing, a zebra-print polar fleece:

The pattern is the Stained Glass Window Afghan from the book
Sensational Crochet Afghans and Throws (I purchased my copy on Amazon). I had to go down several hook sizes (I used a G hook instead of a K, as recommended in the pattern) to get my squares to look tidy. Since they were a tad smaller than indicated in the pattern, I made mine 5x6 squares large instead of 3x4. I followed the pattern exactly up to the beginning of the black border rounds; I noticed that my squares did not lay flat when I followed the pattern exactly and thought that the blanket would bunch oddly when seamed.
I used Caron Simply Soft in in Raspberry, Caron Simply Soft Brites in Limelight, Blue Mint, Mango, Lemonade, and Watermelon, and Caron Simply Soft Heathers in Charcoal Heather (about 11 skeins of the charcoal, about 1 skein each of the other colors).
The fleece backing!A couple of craftsters asked about the backing, so here goes my attempt to explain how I attached it. Please keep in mind that I'm not a sewer, so my verbage may not be correct... and please let me know if this needs clarifying!
1: I laid out the backing, right side down, and smoothed it out carefully so that the fabric was not stretching. I then laid out the afghan, right side up, and made sure that it also was not stretching. It's crucial to make sure that nothing is stretched, because it will cause it to bunch up once they're attached.
2. I cut the backing with a 1" seam allowance.
3. I started to affix the afghan to the backing from the center outwards. At each interior corner where motifs met, I used an 8ish-inch length of the Charcoal Heather yarn and a sharp tapestry needle to join the back to the afghan. I just went through both layers from the wrong side, then back down through both layers about 1/8 in apart. I imagine you could do this just about as frequent as you needed to, if you felt you needed more reinforcement, instead of just the corners of the motifs... but it is a good place to hide it on the afghan side... a lot of seaming going on in that area anyway! I just knotted my yarn on the wrong side and trimmed the ends to about 3in and called these good.
4. To secure the edges I also used the Charcoal Heater, and I just folded the fleecing edge to be in between layers and used a blanket stitch to hold it all together. I used this tutorial
http://stitchschool.blogspot.com/2009/12/blanket-stitch.html.
Here is a diagram, if it helps at all!


The backing makes the afghan much warmer and, in my opinion, gives it a little added durability. After all, I want it to last a long time without warping out of shape or coming apart!
Again, let me know if that info helps or needs revising!