The 5D is a very good camera, to this day. I started with an XTi, a.k.a. 400D, progressed to a 40D, and then the 7D, before I bought my first 5D, in December 2011, to try full-frame digital. To minimize changing lenses, I bought another 5D in December 2012, after thoroughly considering a 5D Mark II. When I do not need weather-sealing, or to track action, I thoroughly enjoy using a 5D, and very much appreciate its images; I doubt that will change anytime soon. Even in low light, the 5D does quite well.
Read DPR's reviews of the 5D and 5D Mark II, and pixel-peep at the comparison section of the Mark II review, showing images shot with both cameras, which will reveal why I elected not to upgrade to the Mark II. I also considered the comparison images in DPR's Nikon D3 review.
I have never used a 30D, so cannot compare it to the 5D. When it comes to capturing images that are pleasing to me, however, the 5D compares well with the 40D and 7D! Life is good!
