Fly123456 - apart from the financial aspects, the SO factor can be a bigger issue than just not taking off or landing.
You will end up doing sims about every 1.5 months - and will often be treated like a cadet during these sims. Also bear in mind that your assessments will count for the rest of your CX career.
When you do eventually get within sight of upgrade to Junior First Officer - you will have to successfully complete the dreaded (and might I add completely pointless) 'Tech Interview' for which guys are doing outrageous amounts of work for (and still failing).
Superfrozo's missive on how little extra you would do in a window seat is bollocks - having gone from the SO to FO, it's a damn sight more interesting - and has nothing to do with ego.
You do get days off - but the Captains and FO's particularly on the 400 get more, and actually get to do something when they go to work.
Just a little more perspective for you!
Good luck.