Good, so far as it goes
I have to admit that I'm not usually a fan of farm-sim games, thus the reason that I tend to avoid the Harvest Moon series. However, I decided to try your game on the basis of a whim once I saw that its overall score had managed to gain it either a green or blue background. The game itself, I find, is simple to play while still retaining a certain degree of a challenge. Towards the end of the game, I began to notice that it was getting harder to meet the challenges set, but not enough to make it frustrating.
I'm rather fond of the idea of building up the farm over time rather than starting with everything already in place. Again, doing so allows you to increase the difficulty level without it becoming too hard at any one point.
However, I cannot claim to be overly impressed with the fact that, as many people have already said, the game is a demo. Yes, I realise that I should have realised that from the start as soon as I saw Totallygame appear on the screen, but that in itself is actually a shame seeing as it has given you a reputation that I am sure you would wish to avoid.
The other game of yours that I've played through to the end would be World Domination II. While that was also a demo, I found it worth replaying quite a few times simply because it still allowed you to play through to the end of your goal - conquering the world. In that game's case, the extra material that you could gain by going premium extended to more characters, weapons and abilities. This was perfectly acceptable seeing as we were still left with a fully formed and intact game. Essentially, it's the gaming equivalent of releasing a few additional chapters for an already finished book.
Sadly, however, this does not apply to Youda Farmer; there is no justifiable manner in which one could claim that the game was finished by the time the demo stopped. To extend my previous book metaphor, it would be like reading through a good novel, only to find that the publisher stopped about halfway through, and left the rest of the pages blank. There is no sense of completion, and thus, no real sense of replay value either.
I appreciate the fact that you may need to rely on the premium upgrades in order to make a living to some degree or another. However, this is the wrong way to go about doing so. As I said previously, you have acquired a reputation here on Newgrounds for releasing, with precious few exceptions, games that do not allow the gamer any sense of completion or achievement. If you wish to go about the lines of premium upgrades, do so in the fashion of World Domination II. Release games that allow people to actually finish what they start, and then give them the option of additional missions, characters, tools, weapons, or whatever's applicable thereto. I strongly believe that your present strategy will only result in you shooting yourself in the foot financially.
You are capable of making very good games when you put in the effort; by adopting your current business plan, you are only selling yourself short when you could be doing so much better.