I often find autocomplete features distracting. I'm a pretty good typist by now, and I generally type by thinking of the word and letting my fingers do the rest. If I can just type something like "restaurant", that's fairly simple. If I have to type "r", then "e", then "s", then "t", then "a", and then select "restaurant", that's a lot more mental effort; similarly, if I have to do something special to avoid typing "restauranturant",
that's a pain.
Some people are very adept with the mouse, and some are really clumsy, and mice aren't the only pointer devices. Some people, including me, find laptop glide pads really clumsy (and are glad it's cheap and easy to buy a decent USB mouse to plug in).
That's not necessarily the problem here, though. If a box always or never needs to be checked, don't display it in the first place. If it sometimes needs to be checked, then you need to have a way to tell the user that that box is the problem.
In general, don't get too fond of looking glitzy and using all the neat Web 2.0 toys. Real people are not difficult to find. Sit down with two or three and watch them try to use your website, and if possible ask them to think aloud. Make notes on what seems to puzzle them and what they don't like. When you make changes, try again with a person or two.
Remember that you can design a website to work with people. You cannot design people to work with a website.