Tablet-with-keyboard recommendations?

I'm starting to do my own research, but let's check if anyone here has opinions:

After being away last weekend, I'm beginning to conclude that my old tablet has run its course. It's an original Motorola Xoom, the first major Android tablet, and while it was pretty decent in its day, it is just plain buckling under today's apps.

So I'm planning to get a new one, but I think I'd like to get something with a good keyboard accessory. I know those exist for iPad (Anna has long been fond of hers), and the new Windows devices seem to be all about tablet-plus-keyboard, but I don't see all that much advertised for Android. There's the ASUS Transformer, which kicked the idea off, but I have no clue whether they've kept that line nicely up-to-date, or what the competition looks like.

ETA: I'm only looking at Android tablets for this purpose. While that's not overwhelmingly set in stone, it's the OS I'm used to, and it's my preference. (Let's not get into OS wars.)

Not sure about size yet -- I'm assuming the usual 10" for now, but could imagine going as small as 8" or as large as 12". Haven't decided yet whether built-in 4G is a priority. (It would occasionally be Very Useful, but maybe not often enough to bother.)

Any suggestions for me to look at?