The S is too big, and you can't really feel the acceleration. Kind of like a big sofa.
Compared to what?
If you compare it to a high performance sports car, yeah, the standard Tesla Model S won't seem all that quick.
But it'll blow the doors off just about anything other than a high powered sports car. It will leave a BMW 328 eating dust, and that ain't a "slow" car.
I suspect most people looking at the Model S are NOT 22-year old males looking to drag race. They want a well built, practical (can actually carry passengers, something most high performance vehicles can not do very well), high mileage vehicle. For those folks, the Model S is more than fast enough.
So if you are looking to DRAG RACE your (standard) Tesla, you'll probably be disappointed. But for normal folks, it has plenty of acceleration (more than you'd ever need).
There are plenty of reasons someone might not choose a Tesla (price, anxiety about battery performance, long term reliability, etc), but I doubt most people in the market for these vehicles will consider "lack of acceleration" one of them.