In MOM 2005 we had seven (10,20,30,40,50,60,70) alert severities. In Ops Mgr 2007 we only have three, critical, information and warning. If you convert a management pack or download a converted management pack you can see in the XML code that for example a rule is genering an alert with AlertLevel 50. If you want to create new views and notification subscriptions for that alert you need to know how alert level is translated to alert severity in Ops Mgr 2007. I did a test with a rule from a converted Biz Talk management pack. I trigged the same rule, but between each test I changed alert level.

Alert Level 70  Critical Alert Severity
Alert Level 60  Critical Alert Severity
Alert Level 50  Critical Alert Severity
Alert Level 40  Critical Alert Severity

Alert Level 30  Warning Alert Severity

Alert Level 20  Information Alert Severity
Alert Level 10  Information Alert Severity

All alert had low priority.