Around eps 3-5 my opinion of Tonbi changed from watchable to good. A lot of it has to do with the humour and Uchino Masaaki who just single handedly drags this show from being a run of the mill try to manufacture as many touching moments as possible dorama.
It got draggy for me from eps 6-8. I didn't really care about Kenshin's story and Yasuo's dad. I just got tired of too many touching moments. On a side note, the Kenshin actor really does Kenshin's 'oro' look quite a few times in this series which tells me that he was acting normally on Kenshin lol.
Liked ep 9 with the marriage bit and I just wanted ep 10 to end as fast as possible. I rate Tonbi higher than watchable due to Uchino Masaaki. His slapstick overacting is a hoot to watch but perhaps a more subdued Kita no Kuni Kara type feel could have worked better. I will definitely try out the NHK dorama special. Too bad there doesn't seem to be any Japanese subs for it. Tonbi is not bad, just depends on how much you enjoy your crying doramas.