First I think it's best I explain where I'm coming from. I currently own this game on Xbox 360 and play with the official fightstick (which works on PC as they're both Microsoft platforms) but have been upset that I'm unable to play my friends who have Playstation 3.
The PC version now being released means that I can now play all my friends regardless of their console preference as we all own PC's (surely?). However saying that Street Fighter 4 is not soft on the specs, you will need a beefy computer to play this with any of the beauty intended. I personally will be upgrading specifically for this as it is well worth it. If you are unsure if your computer can run the benchmark program which tests your computer by showing a fight between Ryu and Sakura.
(Google: 4gamer streetfighterIV benchmark, file size is around 150mb)
As far as the game is concerned, it is definitely the best fighter to come out for years and is currently the best fighting game available. Unlike it's competitors like Tekken and Soul Calibur this game has much more of a skill ladder. Once someone is good enough they will never use to a button bashing mom or nephew, something that happens far too often on Tekken & Soul Calibur. Although this does not mean that the game is not accessible to younger players or newcomers, the game is very simple on the fact but very complex under the hood. This is the best fighting game I've ever played and having been a fan of fighters all my life have a good grasp of the fighters.
In conclusion, This will be a fantastic game no doubt, however the popularity of the game will rely on two things in my opinion.
1. Whether the consumers will have enough power in their computers to run this.
2. There must be a good controller option for players. as using the keyboard would be a disaster. (especially if you're fighting my blanka :D)
If you can address these two areas then you my friend are good to go.