With the Spring/Summer schedules starting to trickle in, lots of minor positive changes and only a couple negative changes coming ahead for Boise in 2013.
Alaska
Boise to Portland: In April, will go from 5x daily to 6x daily flights and the most seats this route has seen since the early-mid 2000s.
Boise to Seattle: In June, will go from 8x daily to 9x daily flights, which if my math is correct is the most seats ever offered on this route by Alaska/Horizon.
Allegiant
Boise to Honolulu: Of course as we all know, nonstop Boise to Honolulu flights begin in February.
Delta
Boise to Minneapolis: In January/February the afternoon flight has been upgauged from a CRJ-900 to an Airbus A319/20 over the winter. Typically this route has been all-RJs during the winter so it's good to see a mainline upgauge. It gets even better in March as the morning flight is also upgauged from a CRJ-900 to an A319/20. It also appears this route is again going to 4x daily over the summer like last year (2x daily CRJ-900s and 2x daily A320s), which is the highest number of daily available seats ever offered on this route.
Boise to Salt Lake City: In March, this route will go from 4-5x daily to solidly 6x daily with the addition of an extra CRJ-900 flight, and in April the morning flight again will be upgauged from an A320/737-800 to a Boeing 757-200.
Southwest:
Boise to Portland: Unfortunately as reported here earlier, Southwest is discontinuing Boise to Portland, a net loss of 2x daily 737s.
United
Boise to Denver: This isn't significant at all, but United is adjusting the Airbus A319/20s on this route to Boeing 737-700/800/900s which will be a tiny seat increase.
Boise to Chicago: Unfortunately it appears that United is ditching mainline service on this route at least for the first part of 2013. The morning flight has been downgauged from an A319/20 to a CRJ-700.
US Airways:
Boise to Phoenix: As in last summer, US Airways will add a mainline flight, taking the route to 3x daily A319/20s over the summer, the highest seat count this route has seen from US.
That's all I can find so far, I'll update with any other significant changes as they come.