Serious Sam HD: The Second Encounter's "co-op mode lets up to four players ratchet up the mayhem across 12 maps that include a brand spanking new Coop Survival mode along with other Cooperative, Versus and Team modes like Beast Hunt, Team Deathmatch, Last Man Standing and Capture the Flag. Featuring BIG guns, TONS of enemies, loads of achievements and more than 100 delightful secrets to discover."
A PC version was released through Steam in late April. The XBLA version will cost $15 (1200 MS Points). The PC version sells for $19.99.
Hopefully we should see a drop in the PC price point.