The greatest limiting factor we will face, or anyone else, for that matter, when trying to go faster from point A to point B, is reaction.
You're driving along a road with potholes in it, it's all fine when you're doing 20 mph. Accelerate that speed to 160 mph, and all of a sudden, avoiding the potholes becomes a feat that not even the greatest race care driver alive can accomplish.
Multiply that principle by about a billion, and you have SOME inkling of what it would be like to try to pilot a space craft traveling FAST. At the end of the day, everyone's goal is to try to develop a way to travel at the speed of light, something we will HAVE to do just to get OUT of our solar system in a reasonable amount of time. What many fail to understand is that, without proper scanning technology. Traveling at light speed is about 186,000,000 miles per SECOND. Each second, you will travel almost 200K miles. Well, there's a LOT of **** that can happen in 200K miles. If you can scan out, say, 2 minutes ahead of you, or, about 25 MILLION miles ahead of you, you're just going to end up as space junk, scattered out THIN.
If aliens have the ability to travel great speeds, then it follows that they also have GREAT scanning technology, the ability to somehow detect things to a fairly high degree of detail and accuracy, at GREAT distances.