Thanks for all your comments guys!
After a lot of thinking I finally decided to go for the DA* 300. Right now I'm very happy that I did. It's an amazing lens! In fact it felt heavier than I'd expected when I first picked it up, and I'm pretty sure an f2.8 lens would be a lot more hassle to drag along.
It's incredibly sharp and contrasty, there is almost too much contrast at times. It was definitely worth its price tag. After just two days of ownership I'd say it's a worthy partner for my DA limiteds.
A few handheld tests has showed me that the Tokina is (surprisingly?) not that far behind in sharpness, but has less contrast. I'd say the DA* 300 has about the same sharpness at f4.5 that the Tokina get at f8
There are a couple of cropped shots of a sparrow outside my house available at my flickr account:
Sparrow on fence on Flickr - Photo Sharing! Sparrow on Flickr - Photo Sharing!