I watched this over the weekend. Really fun and funny show. It's much more interesting early on where it's just a series of incredible anticlimaxes than later with all the hero society stuff, but the show had to go somewhere. I don't know that I'm very interested in a second season given that, though. The parade of anime stereotypes is cute but it's getting played out by the end of the season, and the show should definitely not try to throw up something which actually threatens Saitama.
But the early stuff in particular is fantastic. I didn't find Saitama's own thing about wanting to find a challenge all that interesting, but his aesthetic and his overall attitude towards these anime types powering up and using their super moves and all that is just delightful.
Show's got a notable lack of female characters, and the one that does show up with any frequency is unfortunately anime in a way that isn't being played for laughs.