Just played the first session with Sun "The Cage Potato" Wei.
I had a lot of fun. In combat the Inspire Courage was always appreciated and I enjoyed giving the other PCs ridiculous martial arts advice (e.g., "Damn it O'Malley, hit him with your discipline not with your fist!"). Also, pre-combat buffing with Barkskin made the other front-line monks/brawlers a lot more viable.
He was a surprisingly effective grappler in one-on-one fights although in group fights he tended to hang back and shoot off scorching rays (easily refreshed with drunken ki). Since two of the other monks were so focused on being DPR machines it was easy enough to let them do the heavy lifting, although I expect to put him more in the thick of it in more dire situations that will be coming up. Certainly he's plenty survivable (high HP, very good AC, very good CMD, great saves) and can impact a fight in non-DPRish ways.
Outside of combat the additional skill options from the Sensei archetype were much appreciated, especially when used with the trait that makes a str or dex skill a class skill based on wisdom.
I think the Sensei/Drunken Master/Qinggong monk combination is an interesting one and has the benefit of exercising significant battlefield control while increasing both the offensive and defensive prowess of other martial classes. Scorching ray gives an interesting ranged option and restoration as a SLA saves the party spending a lot of diamond dust. I do have a few reservations about the rules gray area regarding the applicability of Mystic Wisdom to Qinggong class features, so you may want to get an official ruling from your GM before proceeding. There is also a minor bit of uncertainty in which rules system you use for drinking alcohol. We used the system that allows you to drink 1+2*CON MOD drinks before getting sickened. This was more than enough Drunken Ki for my purposes. GMs that use the addiction rules may derail your character by over punishing drinking so beware.