I know this thread is a couple of weeks old, however, I'm excited to let you know that REI has released an updated version of the REI Co-op Half Dome tent this year! It is called the REI Co-op Half Dome SL 2+ Tent with Footprint and is now available to purchase. It still has everything you love about the Half Dome tents: livable space, simple assembly, and the 'plus' length that gives a bit of extra space for tall hikers and/or a four legged friend, however, our designers have managed to shave almost an entire pound off of the minimum trail weight (now 3 lbs 15 oz). Plus, you get great value with the footprint included in the price!
Feel free to check it out and I will tag the other folks in this conversation as well.
Hopefully this helps, come back and let us know what you chose!