This is a game in alpha, every new release, especially when it's adding large new features that break save compatability, is going to be RIDDLED with bugs. This is true of independent games developers and commercial ones alike, its just you never get to see the commercial ones, because they pay people to test it for them. You aren't paying for the game, any money you may give/have given to Toady is your own choice.
While the points you make about lack of compatability with tilesets and various bugs are entirely valid, they should be made in an entirely different manner.
Tileset compatability, for instance, is not even an issue that Toady can consider, they are mods, added by other people. As for the bugs, there are various bug threads and a bug logging system around, you can report issues you may have using those.
At the end of the day, Toady does not have some paid people testing each release of the game before he makes it available, that is what WE do. If you want to play an unbuggy release, wait until after the initial testing period, when some patched version of the release are available. Yes it may take weeks, or even longer, but you have no right to post unconstructive, impolite criticism of it.