Applied for my UID along with Colleagues - Prashant and Saneesh.
Good: The enrollers were very professional and courteous. For a one letter spelling mistake, they re-did the enrollment completely again. Know other govt agencies where even with 100s of mistakes, they say it's fine and don't bother changing anything.
Not so good Experience: The entry part of demographics was time consuming. Retyping so much data in Kannada again was not expected (mainly for word changes like 2nd Cross to 2ne adda rasthe.. etc). The client/webapp kept showing error on demographics screen though all data was filled. The advice from a senior person there : Keep pressing "Finish" and it will take it. :)