I have to be the newest member of the rod building community since I am about 2/3 through my first one. Here is what I have found out so far.
1. It is much easier than I expected after reading a lot of articles on rod building. So far, the hardest part was reaming out the cork grip. However, I worked on it very slowly and it came out just fine.
2. Finding the spine took a bit of practice. I had to do it 4 times before I got the same spot two times in a row. Now that I know what the spine feels like it should be easier in the future.
3. If you file the front of guide feet to a knife edge, the thread will climb right up the foot with no problems; if you don't it wont. I had to cut the first two guides off because I didn't file the feet enough.
4. My first wrap came apart because I didn't use enough tension on the thread. I tightened the tension and was still able to adjust the guides as necessary for final alignment,
5. Building the wrapper and dryer were more difficult than I expected but that was because I wanted a 4 spindle dryer and had trouble finding drive belts. Building the wrapper would have been easier if I hadn't decided a 3 wheel rod holder was better than a felt V rod holder.
6. I haven't done any gluing or finishing yet so it is still easy to correct any mistakes.
7. There is a great 20 part video on fly rod building on You Tube. It cleared up a lot of stuff that wasn't covered in the articles I read.

I thought about buying a cheap kit to practice on but eventually decided to get what I wanted. I'm glad I did because the cheap kit would have been a waste of money.

Go for it! You won't save any money but you will have a lot of fun. Just be sure to take it real slow.