I have started using 2.5.4 for development (as I am using the new $min and $max operators). Noticed performance is much worse than 2.4.x versions.
Apologies if this is already a known error. Have searched for duplicate issue but can't find one.

Criteria:
I am volume testing using pymongo on amazon EC2. Mongod is running on an m1.large instance and I am querying from a separate box within the same availability zone.
Start 100 paralllel processes (each with its own MongoClient). Each process makes 3000 find queries across 3 different collections.
On 2.4.9, I see a throughput of approx 7200 queries / second.

If I switch to the 2.5.4 64bit linux binaries, my throughput drops to around 3500 queries / second.

Performance graphs included. Further info available on request.