Trains, love 'em or hate 'em

[Jason]

I personally like going on trains but the problem is that I am not sure if a montly eurorail pass is worth it.
I plan on spending a lot of my time in London and Paris but I have a month.
How are the schedules?
Are reservations neccessary particularily in the summer?
ANy past experiences or advice on the monthly pass will be appreciated.

[nitsansh]

You definitely don't need a railpass for the time you spend in London and Paris! But where else do you plan to go?