[Sledgehammer427]

From what I know, they were heinously expensive to build (all titanium construction) but even more expensive to maintain.
Alfa/Lira class boats had liquid metal cooled reactors.
let that sink in.
liquid metal
in order to be kept idle in port without the reactors running at critical they had to be kept hooked up to shore power, which kept the bah gawd liquified metal liquidy so it didn't seize up and ruin the entire reactor system
buuuuuuut Russians being Russians..they forgot that simple yet very important step and at least 2 boats are now 100% worthless because someone forgot to plug them in.

Thats all I know.
They were fast, expensive, and kept cool using freakin' liquified metal