STEPS:
1. Upgraded mongodb 2.4 --> 2.6 and I am able to start my nodejs app server without any issue.
2. Upgraded the mongodb 2.6 --> 2.8 and set it up to use wiredTiger storage Engine.
3. Created the user in the test db and authenticated it successfully.
4. Tried to start the nodejs app server.

RESULT:
It fails with the following error. But if I remove the authentication part, it starts up fine. I tried with MMAPv1 as well and it still fails with the same error. I posted this issue in stackoverflow but did not get any answer. Since this is public I can only post very limited information. If you need more information, please let me know, I can email to you.

 2015-01-16T18:43:51.115Z <warn> globals.js:45 () MONGO URI = mongodb://myuser:password@localhost:27017/test
 2015-01-16T18:43:51.178Z <error> globals.js:45 () #### Error in connecting to mongodb
 2015-01-16T18:43:51.180Z <error> globals.js:45 () { [MongoError: auth failed] name: 'MongoError', ok: 0, errmsg: 'auth failed', code: 18 }
 2015-01-16T18:43:51.182Z <error> globals.js:45 () MongoError: auth failed