It depends on you, and as Bob suggests, the apps you use. Some will be fine with OpenOffice/LibreOffice as an alternative to MS Office, some won't. Some people have other "must have" apps that will not run under Linux.
As for the differences, that kind of depends on the distribution you use, but to get some basic idea of what you might be in for, you could download the Ubuntu distribution and try it out. It lets you boot the entire thing off the DVD so there's no installation required. Then you can play around with it a little and see what you think.
Alternately, you could install a distribution or three into a virtual machine a la VirtualBox or something similar. Also a very low risk proposition, since if you don't like it, you just delete the VM and that's it. You'll likely get a better feel for the performance of Linux in a VM, but you'll be less likely to know if there are any potential issues with your laptop's hardware that would become apparent by booting the OS directly. So, you'll probably want to do a little mixing and matching of the two. Maybe boot the install DVD, see if it falls over from lack of hardware support. If not, then go ahead and install it into a VM.
Many people, however, seem to find Mac OS X as the happy medium between Windows and Linux. That is, a Unix foundation with a Windows-ee interface. So that might also be something to consider. Looks like you're probably about due for another laptop in the next year give or take, so if you have an Apple store or something near you, you could go in and play with one a little and see how that grabs you.