Some years ago I used a 721 as the basis of a custom rifle
in 280 Ackley Improved. It worked great. The 721 trigger can be honed to a very nice trigger if you don't want to replace it. It looks a bit cheap, but it works. I'd also recommend putting a Sako extractor on the bolt - my stock 721 extractor went south very early in the project. I stocked the rifle with an HS Precision thunbhole stock, which made it very comfortable to shoot both in the field and from the bench. You would need to custom order it from H-S - there are some subtle differences from the standard 700 stock. I put a Hart barrel on my rifle. It shot 140 Nosler Ballistic Tips very well - 1/2" with the best loads. I also used 100 gr Sierras for coyotes. Very effective.
I later sold the rifle to my deer hunting partner and he has made several 400 yd+ shots on deer with it. I have first right of refusal if he ever wants to sell it.
The 721 is a great action for a custom rifle
. It is just as good as a 700. Good luck and have fun.