There's actually a post on the first page here with some info that might help you. Check for Zergsmasher's question about Talons of the Emperor.
I'll also quote here what I wrote there:
So my commentary will be from a competitive standpoint as I've fielded Custodes at tournaments.
They DO have a place in competitive listing. Sword and Board is the best loadout hands down (though they do have a 5++ without the shields, FYI). The trick is to not treat them like an assault army. They can't deep strike and you're blowing way too many points to load them in a landraider and ship them off to attack. They're bodyguards: wrap them around units and characters you want to protect who can do the ranged damage and anchor them there.
A pure Custodes or pure Talons force isn't gonna cut it either. These kids need to soup. They're the epitome of soup. Celestine makes a great HQ followed by Voldus (to give 3 denials) or any other high volume Psyker.
When working with the Sisters of Silence, I like the Greatsword the best, but the Flamers are likely the most competitive. The Greatsword are redundant with the Custodes and the damage out of the Bolters is pathetic. We're just not in a world where Rapid 1, S4 at 24" is gonna cut it. The flamer squads can at least advance and fire easily to pretend they're Eldar.
That said, Sisters are in a worse place than Custodes. They can and will got shot off the board IMMEDIATELY unless you have lots of LoS blocking terrain. Having 3 squads to deal with Psykers isn't a bad idea, but go overboard at your peril. Conversely, your Custodes should hold up to even heavy artillery barrages for at least 3 rounds. They'll also dominate anything they get in melee (even putting a noticeable hurt on an Imperial Knight).
In the soup theme, Guilliman isn't a bad inclusion. He gives +1 to advance and charge rolls, which benefit Custodes and Flamer Sisters both. Custodes hit on 2's already so re-rolling 1's is a true re-roll misses aura for them by default. It's not bad on Sisters either, though Flamers don't need it. If you can make the ranged power your Talons are protecting Ultramarines, then you've really got some synergy working.
You're not gonna break top tables, but you can push yourself into top 20/100 with this from what I've seen and experienced so far.