I did an overnight test drive of a Model 3 Performance last weekend and my thoughts are below. I currently drive a 2014 BMW 335xi in Sport Mode, so that is my comparison point.
TLDR: I ordered a Telsa Model 3 Performance on Sunday and it beats my 3 series in every aspect.
Driving
While I (used to, the M3P ruined me) love my 3 series from a driving standpoint, the M3P ruined that experience for me pretty quickly.
Acceleration is instant and amazing in the M3P. No lag at all from pushing down the accelerator to the car going FAST. Acceleration in the M3P is unbelievable. Handling is crisp, responsive and beautiful. Cornering is amazing, the low center of gravity from the battery weight in the bottom of the car makes it hug the road so well. M3P beat my 3 series in every conceivable way from a driving standpoint. So. Much. Fun.
Interior
I know the interiors of Telsas are lambasted as not being luxury enough. Our overnight test drive M3P had the white interior and I found it better than my 3 series by a mile. The seats are softer and more comfortable. There is better use of space, giving more legroom and space to everyone, including my two kids in the backseat, than my 3 series. At first I didn't like the minimalistic design of the interior, but after driving it for a couple of days I began to really appreciate it and now find my 3 series cluttered. I think the white interior feels a lot more spacious, luxurious and higher quality. That may not be the case over the black interior, but my family and I felt that way. I also felt that the vegan leather in the Tesla is much nicer than the leather seats in my 3 series, the soft surfaces are much better than the hard plastics in my 3 series and overall more comfortable.
Tech
No comparison here. Autopilot is amazing. I know there is a lot of complaining about NOA, phantom braking, etc. However, compared to my 3 series where all I have is a GPS nav system and parking sensors, Autopilot is awesome. I am am in a tech geek career, so the fact that Telsa adds new features and functionality to the car over time is very appealing. I love the idea that the car I buy isn't static and I get new features for my Tesla as time goes on. Soooooo different than the 3 series. I know there are still a lot of issues with Autopilot features and they don't always work perfectly, but I am excited to help them test and improve. The screen in the M3P is great. I love the usability, performance and clarity.
General
I love that Tesla and Elon has disrupted the industry. I know they don't always deliver on time and what they promise and I am perfectly fine with that. I would rather have them take risks and push the envelope, knowing they won't be able to deliver on everything, rather than have them act like a normal stodgy car company. For this reason I paid for FSD. Supporting the move to clean energy is great imo since I have the means to do so. I also really like Elon going on Twitter and interacting with customers.
Happy to answer any specific questions.