Re: 1080p is it worth upgrading?
I find that the biggest difference comes when I use it to display a PC output. In this situation it doesn't matter whether its 23" or 50", 1080p is required.
Otherwise, for all the things you said you use it for the difference is reasonably minimal. Having said that the new models of HDTVs are probably vastly superior to your set and 99% of new models are 1080p anyway.