A core shot on one of my Mammut Phoenix halves (leaving 45 and 15m sections - I've given the other rope of the pair to a friend) means I'll be needing a new set of half/twin ropes. For ropes of this diameter I think Beal's Unicore construction is a big selling point, and people speak highly of their dry treatment and durability. Now the issue is whether to go with the Ice Lines, which are a similar diameter to the Phoenix (8.1 vs 8.0 mm), or the Gully, at 7.3 mm. For various reasons, I'll be going for 70m versions (greater range climbs without fixed [typically 50 - 60m] pitches, longer simul-pitches with PCD protection, fewer A-threads on ice route descents, and longer rope life if ends need to be cut). This means the full kilo saved with the Gully pair over the Ice Lines makes a bit more of a difference.
The concern, as ever, is handling (control while abseiling, catching lead falls) and cut rope. Honestly, since my first halves were (another pair of) the skinny Phoenix's, I'm used to them and have never had an issue. My belay device is the MicroJul, which should be fine for the Gullies. And since I'll be using the ropes as halves on rock pitches, there is some redundancy for rope cutting.
Still, I'd be keen to hear opinions, especially from any Gully users. How have they been?