Again, normally I'd keep a cover letter single-spaced to fall under a one-page limit. I double-spaced because every other document save the resume is going to be double-spaced. Consistency seemed more important. The word length is not bad and some portion of it is fluffy pleasantries (easy reading but I wanted to include it).
In general, all resumes should have a cover letter. My mom's been an executive placement specialist for years, trained in placing executives, salesmen, engineers, lawyers and the like; this has exposed me to more information on the subject than I'd care to repeat. And I've been involved on the administrative side of hiring, seeing how the firm decides whom to contact and whom to ignore. Both sources of information tell me that cover letters are a valuable asset (in fact, they are virtually a prerequisite at my firm).
Feel free to keep your own counsel here, of course, but why would you give up the opportunity for a cover letter? You don't want to positively inundate the adcoms, since they will spend a limited amount of time per application. But a cover letter is an opportunity to introduce yourself, to explain your resume, and highlight a few of your positive characteristics. It's also more to the point than the PS, which is usually more akin to a 2-page short story than a cover letter. Rather than turn my PS into a utilitarian introduction, I kept it as a way to color my personality and added a cover letter.
I expect the adcoms will be able to read the whole cover letter in 20-30 seconds, and it gives the highlights of the resume in an easy-to-read format. It may actually save time for the adcom while drawing the attention where I want it. I could avoid the cover letter and hope the adcom is able to spend extra time on MY resume to pick out the juicy tidbits before moving on; or I can write what is basically a summary of the relevant experience and help the adcom out. I chose the latter.
I can understand fear of overdoing it for LS, but cover letters are standard practice in employment. A cover letter is both a courtesy to the person forced to read your resume and a method of showing your interest. (For entry-level jobs it also shows that you can communicate coherently.) In a non-LS context, people who don't attach cover letters or some kind of introductory message are often spamming resumes (bigger risk of this if you post job ads in a public forum). It's nice to have an applicant who actually communicates with you instead of tossing out a generic resume without comment or explanation. A good cover letter addresses the stated requirements in the job ad and explains how the applicant meets them; it both proves genuine interest (minor goal) and argues reasons for hiring (major goal).
What would my application package look like without my cover letter?
- My PS is about a personal growth experience and does not address my work experience more than casually.
- My DS is unrelated to work experience.
- My addenda do not sufficiently explain my work experience and are a poor context for doing so.
- My Why X? essay(s) will be too short to mention work and in any case it would not be appropriate to expand on myself in a statement devoted to the school.
A cover letter explains my work experience more effectively through paragraphs than the resume can through bullets and sentence fragments. Also, with all the addenda and statements I'm considering sending, I need some sort of quick document that explains it all. Otherwise I'm just sending a big pile of paper and saying "here, you read this."
Ultimately, I'm less afraid of overdoing it with a few extra paragraphs and a few kind words than I am of missing a chance to frame my resume and application. I also wanted a place to thank the adcoms, and nowhere else seemed appropriate.
But again, feel free to keep your own counsel. I'm not going to spend all day arguing for other people to add cover letters; my application probably looks better by comparison the fewer people who do so.