Well, it kind of depends... If you have just the one game where you charge for the most up-to-date version and leave the previous version free to play but with chance for donation, there's a chance you can run into Garry's Mod syndrome. Which, frankly, is not pretty.
That's where you upgrade a massively popular and previously freeware game and start charging money for it. This results in a massive storm of animosity, rage, geezer-pride and "rebel" servers (if it's multiplayer). This will also split your fan base into people who play the previous version and people who play the new version, and they will both hate each other and try to bite the offending party's legs off at every opportunity.
Furthermore, when people DO upgrade and find a not-entirely-polished version that is less stable (or, heavens forbid, less fun) than the previous -free- version, you will receive massive frustration from the people who just purchased it. This will also make them less likely to pay money for the next version, and will even push them closer to the cheapskate geezers who just complain about the new kids with all their money.
As an aside, people will be far less likely to donate money to you since they feel that you're making enough money as it is off your "commercial" version. Unless the potential price cut for donating would make them pay substantially less than normal consumers, instead of the linear get-in-while-it's-cheap of Mount and Blade (which still isn't finished, dammit).
However, if you are instead talking about releasing Game A as "donationware", and then using the popularity gained from the clever and well-executed idea to spark the drive for the commercially-released Game B, which although being a completely different game, is still coming from the quirky and imaginative developer that brought you Game A (thus hinting at potential coolness), then it's a completely different story.
The people who don't want to pay money for Game B can't complain because it's a different game entirely, and not just an upgraded version of Game A (which they have). And people who feel that Game B is simply not their thing will be more inclined to donate to support their beloved Game A, rather than the mixed emotions that come from both donating to and paying for the same game.
However, people who purchase Game B will most likely not donate all that much, since they feel they've already "done their part". But then again, you got them to pay whatever market price you've got for Game B, so you're ace anyways.
Sorry if I seem to play the devil's advocate a bit, but I happen to be one of the crotchetiest cheapskate geezers to ever haunt indie games and mods. To prove this, I still play Gmod 9 and will likely never upgrade to the heavenly delights of Gmod 10 even though it costs nothing.
The irony involved in certain donation-fueled games is that some people will pay substantially more through donations than they would ever have considered forking out if they were forced to.