Different people in our group tried test upgrades to 11.2. One, using the windows upgrader, got an error:

flow-11.10-11.20.sql : ERROR null value in column "keywordid" violates not-null constraint.

Another, doing a manual upgrade on MacOS got:

ERROR ExceptionUtil 2011-09-15 14:24:16,072 http-8080-Processor25 : Unhandled exception: 500: Unexpected server error
org.labkey.api.data.SqlScriptRunner$SqlScriptException: core-10.20-10.30.sql : ERROR: function "array_accum" already exists with same argument types
    at org.labkey.api.data.SqlScriptManager.runScript(SqlScriptManager.java:132)
    at org.labkey.api.data.SqlScriptRunner.runScripts(SqlScriptRunner.java:103)
    at org.labkey.api.module.DefaultModule.versionUpdate(DefaultModule.java:249)
    at org.labkey.api.module.ModuleUpgrader.upgrade(ModuleUpgrader.java:59)
    at org.labkey.api.module.ModuleLoader.upgradeCoreModule(ModuleLoader.java:620)
    at org.labkey.api.module.ModuleLoader.doInit(ModuleLoader.java:303)
    at org.labkey.api.module.ModuleLoader.init(ModuleLoader.java:215)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:221)
    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:302)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:78)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3666)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4258)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:634)
    at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:561)
    at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:496)
    at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1203)
    at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:319)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:736)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:448)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:700)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:552)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433)
Caused by: org.postgresql.util.PSQLException: ERROR: function "array_accum" already exists with same argument types
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2103)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1836)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:512)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:374)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:366)
    at org.apache.tomcat.dbcp.dbcp.DelegatingStatement.execute(DelegatingStatement.java:264)
    at org.apache.tomcat.dbcp.dbcp.DelegatingStatement.execute(DelegatingStatement.java:264)
    at org.labkey.api.data.dialect.StatementWrapper.execute(StatementWrapper.java:979)
    at org.labkey.api.data.Table.execute(Table.java:189)
    at org.labkey.api.data.Table.execute(Table.java:416)
    at org.labkey.api.data.SqlScriptParser$Block.execute(SqlScriptParser.java:164)
    at org.labkey.api.data.SqlScriptParser.execute(SqlScriptParser.java:61)
    at org.labkey.core.PostgreSql83Dialect.runSql(PostgreSql83Dialect.java:719)
    at org.labkey.core.PostgreSql84Dialect.runSql(PostgreSql84Dialect.java:24)
    at org.labkey.api.data.SqlScriptManager.runScript(SqlScriptManager.java:127)
    ... 33 more