Plant Tycoon, and its sister programs like Fish Tycoon and Virtual Villagers, are one of the few games I've bought where I bothered to go to the fan website and speak to other players / put up my scores / and wait for release dates.
I read alot of reviews that complained about its graphics being poor/blurry, but I've had it nearly 12 months now and I'm still not finished and still enjoying it (al-be-it to maniac proportions now). The only annoying things are the wait on being able to grow on the more exotic plants that you may create earlier on, and the fact that the program doesn't keep score of which crosses you've already made, so you actually have to keep all that yourself somewhere. I'm using Excel.
I've found lots of different flowers and plants throughout the twelve months, which is why, I guess, I'm still playing it. Just when I think I've got them all, another new one pops out of a cross.