I've heard Gergiev conduct live several times, orchestral and opera. Not a large sample size, but I was never very impressed (this was in NYC, Gergiev got huge profiles in the N Y Times, and I recall thinking that he had a great press agent). I have a couple of recordings, but based on my live experiences I didn't pursue more. At that time, I found that he had a lot of passion, but the performances were sloppy, and I speculated he might have been spreading himself a bit thin, as he was doing an exceptional amount of globe-trotting.
Disclaimer: My experiences were on the order of 20 years ago, so I have no idea how Gergiev's career has evolved.