A cover letter is your time to shine, please please don't ignore this golden opportunity.
I've looked at CVs, and in the case of programmers (and you appear to be one) they are a wall of stuff i don't want to read. Pygon1! J2EEEE! Roonix! Ciscows! None of which reads, it's just... words.
Some of them might be pertinent, but fun fact - a lot of people have your experience, whatever the language. The language is rarely used unless there are a lot of developers (think bank database systems for one of the "rare" examples).
But the cover letter... ahhhhhh, the cover letter. You get to explain who you are. Are you ambitious? A go-getter with natural leadership qualities looking for a place to grow with? Someone with excellent communication skills and a burning desire to produce great code?
The resume is your gateway into a technical (or any other) role. It is where people get to see what your past experience is, and whether your experience aligns with the skill set the job needs.
For tech roles, you don't really need to sell why you are passionate about investment banking, or formula one cars, or children's books - although that is certainly really helpful, and if you can do it, do so. For non-tech roles, selling yourself and the domain the company works in is more important, but...
More importantly is to stress you inter personal skills, and what makes you tick. I have a section on my CV that mentions my hobbies - just to make me more human. With a cover letter, you get to do that and more.
Don't look at the cover letter as a hindrance - it is an opportunity to paint a gorgeous, 3d technicolour picture of who you are, and the kind of leader you want to be. You will stand out 100 times more than all the other candidates, and everybody will want to interview you - who wouldn't?