Pretty much all of Burnaby with the following exceptions: Metrotown, Brentwood, the Highgate/Edmonds area, along Canada Way, Burnaby Heights, University Highlands (Burnaby Mountain). Or, if you're walking distance to an Expo or Millennium line stop, that's also okay. Also, the Lougheed Mall area, but avoid the low-income apartments west of Government Street. ("Lougheed Village")
I should bring special attention to the #129, which is the #22 of the suburbs. It's a long route (25 kilometres) that goes through some of the most congested roads in Burnaby. Ever since the route increased to 12 minute headways during rush hours there have been some improvements, but there are 30 minute headways during non peak times and 60 minute headways after 10pm; traffic doesn't stop at 6pm, however, so the 129 is either unreliable or infrequent or both. I don't like the 129. Other areas with underserved transit or low penetration include: Big Bend, South Slope, Suncrest, Cariboo Hill, Lake City/Montecito, Parkcrest, Forest Grove.
Pretty much all of New West with the following exceptions: Around 8th Street, around 6th Street, or if you're close to a Skytrain stop (again.) Specific areas to avoid: Sapperton/Brow of the Hill (unless you're close to Skytrain), West End down to about 20th Street, anywhere within a 3 or 4 kilometre radius of McBride @ 8th Avenue, Queensborough unless you're near the #410.
Tri-Cities: Heritage Mountain, Maillardville, Noons Creek, Westwood Plateau, Burke Mountain, Cape Horn, Mary Hill, and all of PoCo. However, things should improve significantly with the Evergreen Line.
South of Fraser: Oh boy, where to start. 112th and 116th Street in NorDel (312/316), 96th Avenue between 112 and Scott Road (314), 128/132/140 Street (323/324/325), anywhere around 108th (329/332/335)...the list goes on and on. And don't get me started about Langley! You might as well drive unless you live close to 200th, 88th or Fraser Highway. Of course, no one living out in Langley would try the Downtown or UBC commute...right?
Richmond: Everywhere unless you're close to Bridgeport or Richmond-Brighouse (403, 405, 407).
South Delta: That place still exists?