I do not see anything bad about it. I did the same for Gemini Wars. If you genuinely think, the game is really good (or going to be really good), its natural you want to tell other people about it... at least you support the developers this way by spreading the word. If you really believe its deserved and you do not do this for money, its nothing wrong with it.
BTW i checked the game and it looks interesting, but apparently its a variation on tower defense games, right? I am not sure that this is my "cup of tea", but maybe ill give it a try and download the demo.