In a nutshell, the Formula Pro dispenses 2, 4, 6, 8, 10 ounce bottles at the optimal temperature. We use a few different style bottles of various heights and it works for all of them. In the middle of the night I get up, pop a bottle under it, press a button and presto! The water reservoir needs to be filled about once per day and the formula bowl needs to be filled every five days or so (obviously, this is all dependent on how often/how much your baby eats). Check out this video for a more detailed look.
One thing I have noticed is that the dispenser area starts to get a little clogged over time possibly resulting in less powder being dispensed into the bottle (we learned this the hard way when Ben seemed to be eating a TON!) We now do a little preventive maintenance each time we fill the powder and clean this area out.
Besides that fault, I love this thing! It's nice not to have to measure out scoops six or seven times a day. There's no messy powder on the counter (except the once a week that it gets filled). Bottles are always warm. One thing I do wish this fancy thing would do is make a one ounce bottle. Ben is currently drinking around five ounces at times. To combat this we make a two ounce bottle and add an ounce to the bottle. We then refrigerate the extra ounce and add it to the next bottle (sure, it cools it down a little, but not much).
So, though this is splurge, I recommend it if you are a formula feeder and are a stay at home mom or are planning to take a significant amount of time off of work after the birth of your baby.