By the late 1990s, most microwaves had turn-tables in them. This was to prevent standing waves from heating up specific points within the oven, while ignoring others. It's better than nothing, but it's still not perfect.
There's a newer system in some models where the cylcotron itself moves, so that the food can remain stationary, and they can better control how the hot spots / dead spots move within the oven. I've personally never used one of these new models, so I can't comment on how well it works.
Other recent-ish features that you might be interested in are what my model calls 'turbo-defrost', where you tell it what weight and type of item you're defrosting, and it runs through some prepared plan. (in some cases, it'll beep and ask you to separate things ... eg, for chicken pieces).
Some also let you chain commands together -- so you can tell it to defrost for 5 minutes, then switch to 50% power for 2 minutes, then high for 2 minutes. (I find it to be more confusing than it's worth; you might be more comfortable using it)
There are also 'combi' ovens that can defrost via microwave, then switch to conventional oven to get some browning. (I've never used one, however).