No. You are not able to update past ios5.1.1 and the ipad 2 and above are updated to the latest version ios6.1. This means you are unable to load any program that is written in the higher software version.
It depends on what you are trying to do. The operating system for the iPad 1 can only be upgraded to a certain point and you are not able to upgrade to the latest version released by Apple. Depending on what you are using this device for this may not be an issue. I have three iPad 1s in my household used for media playing (movies, music, etc.), internet, e-mail, and light gaming, e-book reading, and they are absolutely fine for those tasks. The later generation iPads also have some hardware upgrades like cameras that you can't get on the iPad 1. If not having cameras on your iPad is not a big issue for you then the 1st generation may be just fine for you. At the end of the day it comes down to what you are wanting to use the device for. If you are not a power user, don't want to do heavy tasks with it, and just want the basics it certainly still works...despite what some may have you believe. :) Hope this is helpful!