While we have yet to put anything in production, during our POC of Monitor Solution, we did a few "SNMP Get(s)" to monitor CPU and Memory utilization on a per LPAR basis. So you can certainly expand on this approach. There should be quite a bit you can get out of SNMP Gets.
Trap receiving is a different story though. We found, even with the correct MIBs loaded, we could rarely interpret the traps.
Another approach we are working on is "Remote Command". This is a utility included in the connectivity tools for the AS/400 on Windows. It allows you to run various commands within the AS/400 and return those results to your command window. This is where we want to end up, but simply have not had the time.
Right now, we run a few scripts within the AS/400 to monitor for error states. We want to continue to use those, but run them perhaps from "Remote Command"; or you can even use ODBC.