I was juggling between MySQL and Postgres, but after playing around with both of them, I kind of like Postgres the best.

The question I was posing really is surrounding a separate project that I will be starting after this one. It is a POS system and networking is ALWAYS an issue with these people. So like you would have register 1 recording sales for itself and register 2 doing the same. If the server went down, you would like the computers to continue to process sales flawlessly until the server came back up online. I was thinking that ideally the register would run off of their own database, so that way if the server does die, then it will never effect the registers performance. However that sales thing is sticky point because I dont think that replication will work very well with it.

Then you have to add the layer of having multiple stores.....

It is funny you brought up the online cloud. I have a plan laid out for actually designing and creating a complete POS system on a cloud @ a cheap price for small companies that cant afford a big system or the little guy that travels a lot and has access to the web.