A good SLR might be cheaper than you think. For example the photo of the leaves falling that you like was taken with equipment that would now cost about $500 (Nikon D80 with Nikkor 50mm 1.8D lens). It depends on where you live. If you live in Tokyo, you have great used gear options. I almost always bought used lenses when I lived in Tokyo. No reason not to. Much much cheaper. Even a used SLR body is sometimes ok.

The learning curve takes as little as your excitement level. No doubt if you have no one to give you pointers, it can take a few weeks perhaps before you get one good image you like. But if you read the manual and read a few key photography websites for tips and study the settings of photos you like on flickr, you can learn pretty quickly.

Give the DSLR world a try!