I consider myself an "upgrader"
I, too, recently traded in my BMW 330xi for a Prius. While the car clearly does not handle like a BMW in either cornering or acceleration, it certainly handles competently. Strong crosswinds on the highway are the only real issue I have with handling. In terms of creature comforts, I'm also going to really miss the heated leather seats in winter.
On the other hand, there are LOTS of things I really like about the Prius. The gas mileage is certainly one of them. In my typical mixed highway/city driving I was averaging about 23 mpg with the BMW. If I drive to maximize mileage, I can typically get 50-51 mpg in the Prius. If I drive more aggressively, more like a normal car, I typically get 47-48 mpg. The thought of sending less of my American dollars to the middle east certainly gives me a warm and fuzzy feeling inside. I actually enjoy driving the car for high mileage. I like hearing the complete silence at a stoplight, and knowing that when I'm coasting/braking I'm not generating wasted heat but useful electricity.
The smart entry/smart start is wonderful. I highly recommend it. In fact, if you can afford it, I'd recommend the BC package with Navigation, the CD changer, and the rest of the goodies. I find it constantly entertaining. What do I do first? Check the mileage? Wach the split screen navigation readout? The upgraded stereo doesn't sound as good as my old system, but I find it much more logical/user friendly than the BMW's. It's the little things, like being able to simply push the FM button to turn on the stereo and play the FM radio, or putting a CD in and having the stereo come on and play the CD. Or being able to fast forward a track on a CD without switching to "manual" mode. The BMW sound system was completely illogical. My CDs would skip all the time when I hit a bump. Having an antiskip buffer has been a part of CD players for a LONG time, but apparently not yet discovered by BMW. NO skips in the Prius.
I LOVE the cabin storage spaces, another big BMW weakness. TWO gloveboxes, a LARGE storage space in center console between the seats, a small hidden drawer on the front of the center console and ANOTHER storage space below the CD changer. AND a LARGE sunglass holder. I also now have TWO cupholders in front without having to fold up my armrest (very annoying on the BMW) AND I have cupholders in the back for my kids.
Speaking of the back, I can actually fit my three kids in the back seat without complaints! The back seat is substantially larger than in the BMW 3 series. Front seat room is also significantly greater.
The hatchback is very functional/useful. Much more so than the trunk on the 3 series.
The climate controls/system is MUCH better on the Prius. The air conditioner works better. The temperature settings actually make sense. I used to set the temperature in the BMW to 64 degrees or less to feel like it was actually cooling the car and I could never get the car really cold on a hot day. Hitting auto in the Prius actually turns on the air conditioner, unlike on the BMW AND it intelligently sets air recirculation. What were those Germans thinking?
The BMW was a lot of fun to drive, especially when you pushed it to its limits. However, driving the Prius makes ME feel good. I don't race to get where I'm going and have become a much more mellow driver since getting the Prius. The loss of handling and heated leather seats I find to be more than compensated for by EVERYTHING ELSE about the Prius. My BMW salesman told me that once you drive a BMW, you never go back to another car. Despite its flaws, I really liked my BMW and thought he was right. Right up until I tried the 2004 Prius. Once you drive a technological marvel like the Prius hybrid, you'll never go back to a normal car.