This is what I like about Canon Rumors. You people out there have so much knowledge and if someone says something technically incorrect it can corrected immediately.
My personal experience is moving from 15MP up to 22MP.
Initially I thought I wasn't seeing much difference in resolution and was wondering was it all an illusion that higher MP was better. What I am learning as time go by is that full frame can give certain really nice aspects to the photo like in terms of depth of field. I can't recreate it on the APS-C sensor. When I go back and forth between the two cameras I start to notice the subtly better resolution.
I may be like alot of people in that you are always looking for more resolution, hoping the small guy way in the distance could actually be zoomed into and be recognised. You hope that a higher MP camera would provide you with this. There is possibly a diminishing return element in so as far as how good can it get.
File size is an issue with 22MP. Unless you upgrade your PC everything slows down. The uploading to PC, the processing and saving all takes longer. Storage becomes a more serious issue. 1 or 2TB Hard drives don't seem to big any more. In fairness to Nikon the D800 seems to be quite impressive but I think I would start to find that file size a little troublesome to deal with. You'd have to upgrade your PC and storage with it.
When the Canon 5d Mark IV comes out and its 48MP will I be tempted. No doubt the dream of greater resolution will tempt me but I will have to consider all the surrounding costs as well.
Master the 5D Mark III first I guess and see can I reach it's limits (like I did with the 500D/Rebel (something something) - which is still a great camera) .
Keep up these great conversations. You lose me at times with the details technical specs of sensors and lens but it's very interesting
If you are bored you can skim through my Flickr Page. It's not brilliant but I think I am improving slightlyhttp://www.flickr.com/photos/fergalocallaghan/