There was definitely some wifi drivers problem in the original Lion. I wrote a fairly popular blog post summarizing reported solutions to the wifi problem in Lion and what solved it for me: http://thoughts.maayank.com/2011/08/wireless-problems-with-m...
I wrote it a long time ago, but maybe it will still give you (or others) leads to a solution. FWIW I haven't had any major wifi problems since the first or second Lion update.
That matches my experience, too. I had dropping problems when I got my MBA (mid-2011) and it magically fixed itself sometime after Lion shipped. I have no problems now.
It was a major disappointment for me at the time as after years with Linux I bought a Mac exactly because I wanted to focus on my work and not on solving fringe kernel issues. Luckily, no major problems since then.
I wrote it a long time ago, but maybe it will still give you (or others) leads to a solution. FWIW I haven't had any major wifi problems since the first or second Lion update.