1) I agree that you can't rely on the Acela schedules. While the trains frequently run on time, they just as well can have 30-60 minute delays. That can be in good weather or bad weather.

2) I disagree with the taxi recommendation. Unless you are arriving at an off peak time, the wait for a taxi can be lengthy, particularly if weather is bad. Any reputable limo service can pick you up at Penn Station. While they won't have a meet and greet service, the red cap can take your luggage up to the street if you need help. I think having a car service waiting is a big plus.

3) Be sure to opt for first class on the Acela. The extra cost is nominal, and you get a hot meal, wider seats, more legroom, use of the Acela lounges (and preboarding if you use the lounge), and other amentities.