The reason you don't want to dilly-dally about pruning spring-flowering shrubs is that the spring bloomers will be setting their next year's flower buds in June and July, and if you wait till then to trim, the shrub won't produce any flowers the next spring.
Shrubs that bloom on new wood include lavender, common sage, santolina, butterfly bush, blue mist shrub (Caryopteris), beautyberry (Callicarpa), most roses, some hydrangeas (arborescens and paniculata), vitex, and rose of Sharon.
Most of these shrubs benefit from pruning out winter damage and crossing branches, as well as reducing their size. I want to see the butterflies that sip from my butterfly bush. If it's 15 feet tall, I won’t see them.
This is not a good time to prune roses [pdf]. Roses are cut back pretty severely in my yard, and I don’t want bitter temperatures to descend after pruning and kill any remaining tissue. So I let roses wait until some real warm air appears and the bushes start to leaf out. Diseased, dead, damaged stems get removed as well as stems that head into the center of the bush. (Note: A few roses bloom on last year’s wood, like many heirlooms and the New Dawn climber. So – prune them after blooming.)
Many evergreen plants can be pruned now as they are going to be coming out of dormancy soon and will begin to grow again. Boxwood can wait until late April to be pruned.
Cleaning up winter damage will be important this year. Cracked and broken branches can be pruned out carefully and most plants will recover well. Cut back to a leaf node rather than leaving a stump and your plants will be happier. Step back frequently to see how well balanced the remaining branches are. And stay off that ladder.