Very nice! Good color, clean, and readable. It looks like the highlights in your mountains got a bit blown out—there's not nearly as much visible detail on the sunlit sides as there is in the shadows. I think you could use with a bit less contrast in the mountains' shaded relief.
I'm not sure what's going on with that lake in the mountains. It looks as though a river begins in the foothills and climbs up to empty in the lake. It's possible that the river actually runs from the lake into wetlands, but that isn't how it appears, and the wetlands would probably occur out in the plain, anyway, not in the hills. In either case, that's an enormous lake to be found in a mountain range like that.
For forests (I am assuming that since you're following Jezelf's tut that you're using Photoshop), try a small, hard brush with scattering in both axes set to maximum. Set your foreground color to a dark green and paint in the forests on their own layer. To add just a little bit of depth, use the Bevel and Emboss layer style. I like an Inner Bevel with Depth at 1% and Size and Soften both at 1 pixel. You can adjust the settings to taste, but I think very subtle is usually best. Set the Highlight color to light green and the Shadow Mode color to very dark green. That should make it look a bit less plastic. If you want to add some color variation, add the Satin layer style, too. Again, subtle is best; you just want a little bit of color variation.
If you want your relief to show through, make a copy of the relief layer, set the blending mode to Overlay, and put it on top of the forest layer. Right-click the layer and choose Create Clipping Mask. Then adjust the opacity until you get the effect you're looking for. You might also want to blur the clipping mask a bit to take out some of the detail.