The noise issue you are seeing is most likely due to the greater pixel density of the 50D. Denser sensors tend to produce more noisy images due to the signal/noise ratio. However, your output isnt the same size due to the greater MP so you have to take comparing 30D to 50D images at 100% with a grain of salt - many are noticing this with their 7D's. Just print them out, you wont notice it at all. Im not sure about your settings b/c I dont have EXIF viewer at work but try shooting at ISO 100 from a tripod.
The reason you're not getting that ethereal forest feel is because it just wasnt there to begin with but I can see you were hitting the golden hour in these photos, but you just didnt nail the composition to show it.
For example, in number 1, all of that golden light - the part we are interested in - is stuffed into the upper right corner. Your shot definitely had the most traditional composition, but unfortunately that comp emphasized the 3/4 of the image where we see mostly shadows. We want to see more of that golden light - I might have tried to get to the right side of that stream to emphasize this light.
#2 - I know what you were going for in this shot because I want to shoot stuff like this around my house all the time. But, unfortunately, what you were feeling in this spot just didnt come across in the image. Could be the composition, Im not sure - but its really just not that interesting to look at. Plus, the whites are blown in the snow and everything else is just a bit muddy - I might have taken the exposure down a bit and/or toyed with this in PP a bit more.
#3 - I feel is the best of the bunch and Im not going to nit pick this image. Nice shot.