Just come back from test centre with a pass on my ONT exam and after 8 gruelling months of study I am finally a CCNP.
Many people think the ONT exam is the easiest due to its sheer lack of material, however I don't agree (having just sat the exam!). Where the ONT lacks in material it makes up in the thickness of the material needed to learn. Frankly and with any exam, if you know your stuff you will find any exam easy.
Took me 8 months from start to finish and looking back now I feel with a bit more determination and better planning I could've achieved this sooner.
My approaches with all 4 exams were Ciscopress books, Bryant Advantage, CBT Nuggets, Switch / Router simulators and creating my own practise tests using flash cards.
Onto CCVP now starting off with CCNA Voice, will use the same method above.
Good luck to all who are studying for the CCNP, I can say it isn't an easy road but a great achievment once gained.