I have to disagree, partially. While I agree that sentient, technology-using aliens at roughly our technological level would be intelligible, I'm not sure such beasties exist. Not within our galaxy, possibly not within the Local Group.
Notwithstanding my personal belief that the evolution of life beyond unicellular non-eukaryotes is a fantabulously rare event, we only have to look at the timescales involved.
Given that it takes approxiamately 4-6 billion years to synthesize spaceship builders from amino acids, and that we spent 3 of that 4 billion evolving nuclei, and that becoming multicellular is very difficult, rare and complicated, I'd be very surprised to find any aliens whose development is within 100 million years of us, much less 100 years.
And wouldn't 100 years be enough for extreme differences anyways? 100 million years ago we were what? Squirrels? Or amphibians? 500 million years before that we were cells. 100 million years from now, we'll either be dust or Powers. Call it a lack of imagination but I don't see a third alternative.
My personal suspicion is that there are exactly 2 types of aliens out there; paramecia, and Gods. :)