One summer of research

Is it enough, sure. Is it going make you a strong research oriented candidate for top programs, no.

 

It's more important to be able to explain what you got out of the experience (i.e. were you just washing dishes and autoclaving stuff or did you have some role in hypothesis testing).

 

Do you have anything else you could/would rather be doing? If you're planning on applying to a bunch of research-heavy schools, you should definitely do it. Otherwise, it would be better if you find something else (volunteer-oriented) to do that you think you would actually like. It's not too late to be applying to volunteer things right now. One of the best things I've ever done was volunteer in a free health clinic.

You can actually get a lot out of it (research) for yourself, for your application, and for the interviews. I had two summers worth of research experience and it was more than enough to talk about.