I've been using the Times Reader application on and off for a couple weeks now, and overall it's very nice, though there are some annoyances. I first read about the reader in an article on Slate, which raved about the readability of articles inside the reader. I agree that the text rendering and automatic columns in the reader make a huge difference, especially for long articles. Also, being able to read offline is really nice. On a recent flight, I was able to read most of the Sunday Times without having to flip pages on a crowded plane.
There are some problems, however. Although the Slate article claims that a week of the paper is stored, I've found that articles are deleted within a day, which is actually really annoying. Also, I've found that certain articles just never appear in the reader; I assume this bug is fixable. For some reason, the reader consumes an obscene amount of memory, often more than 100MB. This isn't a deal breaker, but if reading 5 papers through similar readers requires 500MB of memory, then that will be a big problem. Finally, it's annoying to be separated from the web while reading the articles; I don't see the most-emailed articles list, and it's harder to quickly search for something on Google or Wikipedia.
Anyway, if you have Windows, the reader is definitely worth a look.