Here's a review of Flash Duel from what my Finnish friend describes as "the biggest boardgame website and authority in Finland." You might need Google Translate.
And for an American take, here's Fortress Ameritrash's review. Both sites said 4.5/5.
And while we're talking about Flash Duel, both versions are on sale at Amazon for a week for US customers. Deluxe version $39->$29. Regular version $15.99->12.99. Usually I'd say it's better to buy from my site, but Amazon has this crazy policy where they automatically disable your seller account over the holidays unless you sell 25 copies of something during September and October. I can't sell Yomi there yet because it's not manufactured yet, but I won't be able to list it there over the holidays unless I sell some Flash Duel there now. So now would be a good time to help out! Yeah it's weird. And again, this is only a US thing.