I've enjoyed it. The animation's pretty scrappy at times, and Lion-o can grate, but on the whole I think it works. It's harmless fun, and pretty charming.
I'll always prefer the original - i loved the sword-and-science mix, with Moebius-esque characters and the mystery of Third Earth's past.
But like TTG, TR works like an affectionate parody of the source material, like those 4-panel gag mangas that are produced in response to popular video games in Japan.
Just view it as a companion piece to the original. Chill out and enjoy it. I genuinely didn't think I'd ever see any new Thundercats anything after the last reboot, so this isn't a bad result.