The 24mm/2.8 OM Zuiko is an excellent lens. It is razor sharp and has great contrast and color rendition. I have read contemporary comparisons of this lens to its big name rivals and it topped them all.
The 28mm/2.8 is nearly its equal with less perspective concern.
And the 28mm/3.5 is probably the best travel/street lens. In daylight set it to f/5.6 or 8 and pre-focus for 4-30ft. Makes an excellent point-and-shoot. Shoot from the hip and never miss a shot.
For a great street setup, an OM-10 with auto exposure and a 28/35. can't be beat. If you drop it, lose it, or it gets stolen you won't be out a whole lot of $$$ (but you will cry over the lost shots still inside)