right: MUNI does suck, I use it and I know.
The biggest bang:buck will be upgrading the wheels, I don't know exactly what Ukais you have, but they are probably the OEM. Maybe keep them as a 2nd set and spring for something really nice and in tune with good tires.
The brakes are sort of cheepo, but nearly all road calipers mated to mtn. brake levers work really well. Rather than some pricey vintage sidepulls (which we all like, of course), why not some modern dual-pivots with fresh Koolstop pads? That's going to give you enough grab to stop on any SF hill...well, maybe