I was just there in February! I wrote a lot on it in a tea blog, which I'll cite one post of here, and also ramble on a bit:
The post entries were on black tea (that one), yellow tea (which I mentioned in another thread here), more on travel in Seoul, and one on online research prior, so only two were really review-themed.
What to say about Korean tea? I've only actually tried three, so it's almost all extrapolation to say anything, beyond summarizing what other people said. We were just in Japan on the same trip and I bought 4 teas from there, and 4 from China (couldn't not buy them in the Yokohama Chinatown), and the vacation definitely wasn't about tea, so it didn't get far.
Koreans are really into tisanes more, and it's much easier to find tea shops as cafes than dry tea shops, so aside from grocery stores not so easy to come by tea. I'd have loved to have went a bit further and dropped another $100 on over-priced Korean teas to get the full story, but the sticking point was the need to waste another full day of looking in Seoul, or at least half-day. The vacation theme was about amusement parks and trying to cover two countries in less than two weeks was a stretch. Luckily we'd been to both before or logistics would've overwhelmed us, but it was tough as it was.
You'd think Korea might be way too cold to grow tea but apparently not. I was there in winter once and it was bitter cold, plenty cool enough to kill any tea varietal, but then I guess in the far south out on Jeju Island or somewhere tucked away maybe not. They have their own tea tradition but it's not like China or Japan (or wherever else, Taiwan, Sri Lanka, etc.) where people are always drinking it. Come to think of it in China coffee is perhaps more popular with urban younger people, those in their 20s and 30s, but I digress.
They generally prefer green tea, so I blew it by buying a yellow and black tea in the better shop I was in. The plan was to keep looking, which I did, but the green tea I bought was a bit sub-standard, in a traditional market area where I'd hoped to also find dok-cha, their compressed tea version (like pu'er, but not like pu'er--which I didn't find). Those teas were interesting, and sort of nice in their own way, but Chinese teas are so good and diverse across a broad mid-grade range that the bar is kind of high just to be decent elsewhere.
I had great luck in Vietnam with that (another tangent), but in Korea I needed more exposure to get to teas that really rang a bell. I stepped into a couple tea cafes that were on the amazing side, rough-edged but homey wood-panneled places, or a tiny spot with a cool stove and seating for only about 10 people, if they were friends, with wonderful smells of sweet herbs from all the odd mixtures they were drinking. Given I was pressed for time I stepped right back out of those places looking for some elusive loose teas.
I like to leave a bit undone when I vacation to serve as a goal for next time but in Korea it was too much, and in Japan too, I barely got started. I found an elusive black tea there (wakoucha), and was introduced to hojicha (roasted green tea; I never said I was already a tea veteran), but there's another thread here for that, and I'm short on details there too.