Before an injury happens, I'm not rooting for it, but when another team's player gets hurt, I'm happy with the advantage it confers the C's. The Celtics are in year 4 of this championship window, and have had significant injuries in 3 of the 4 years.
2008: healthy = title
2009: KG out, Powe out, Miki Moore and Scal playing serious big man minutes.
2010: Perk injured ACL game 7, plus various other ailments (including a limited KG)
2011: Perk out, Shaq and JO out most of the year (that's expected IMO, just not to this extent), Marquis out
I never subscribe to the "if not for injuries Cs wouldn't have one" take, mainly because my mom taught me "if wishes were horses, then beggars would ride"