I know JPM off the QHYCCD/Cloudy Nights forums has a Tokina 300 F/2.8 the same as my old one... he's taken many many fantastic images, and secured 2 APOD's with it too... His has proven to be EXTREMELY good for imaging... pinpoint stars across the full field of the QHY8 chip, extremely sharp @ F/2.8...
They cant be beat for a supreme wide field imaging lens... Just look at Bert/Scotts work with Berts 300 F/2.8... They are godly lenses...
(Im still yet to let my 500 F/4L loose on the stars (I dont like the idea of it being mounted on the scope through all hours of the night... My baby might get damp..... or catch a cold... No!!.. it spends the night in bed with me
)