I'd definitely check out the ratings from Consumer Reports that are
available online. I disagree with the advice to go with a unit with a
mechanical timer. These are the cheapest units, they look like crap,
and I doubt you will find that they are any more reliable.

One thing I would look for is a flat panel design that is easy to keep
clean. I personally would avoid units that have hidden controls that
are located on the top door edge. That seems like a very bad place
for a touchpad, as it gets hit with steam, water occasionally.

A lot of it comes down to personal preference. Stainless interior
looks a lot nicer, and it's sold as being unstainable, while plastic
supposidly can pick up stains from tomatoe sauce, etc. However, I've
had both and the plastic one didn't get stained.

I would't pay extra for a lot of cycle features you will never use.
More important is how well it loads, how easy it is to remove the upper
tray to fit really big things in, etc. Some units have an upper tray
that you can lower if you want increased room up top. I think a couple
of Maytags had this feature worked out really nice, where you could do
it quickly from just grasping the side handles. But again, how much
you would actually use it is questionable. I think noise is an issue
that is very important and again CR has those ratings.