Tactically, I think Valverde is good, just not Barca level.
I'd say Valverde has some clear qualities. He is calm and composed, and over 38 games this shows up, because the team is successful at playing in a game by game basis, which gives us the much needed consistency to come out on top after a 10 months battle. His Barca is, so far at least, a very very hard team to beat in the long run. You can't have this kind of consistency unless you do some things about your job really well.
But has 2 really big flaws I can't get over, because I get the feeling that these flaws will never be eliminated.
1) doesn't care or doesn't know (or both) to develop talented young players because he is so conservative that he basically thinks every young player is the same. Older players are automatically more ready to cope with pressure than young players, so he basically values experience (this is very related to age basically) over talent and potential.
A guy like that could have Busquets circa 2008 and he would stall his development for 2-3 seasons making him a bench player, getting minutes here and there in a sporadic manner.
2) doesn't have anything special in terms of vision. Doesn't play a very good brand of football, doesn't have a great football mind that is helping him to bring his best tactics in the bigger games, doesn't have great leadership skills. Doesn't have a very coherent style of playing that would make him stand out among other managers.
That being said, if he wins La Liga or CL this season, his results will be noteworthy after two seasons. Not unbelievable or anything, but good. If he wins the CL he will make a name for himself, but I doubt he will, because somehow in CL he has more flaws than qualities. Basically, just like league campaigns bring out some of his best qualities, Champions League high pressure intense games bring out some of his most visible flaws.