Twin Air is nice, it's a little smaller than stock, which means you can pull it out without scraping all the dirt off on the sides of the airbox.
No Toil stuff is nice, cleans up very easily and is enviromentally friendly. Just don't use it on UNI filters! The glue on mine fell apart, then a little internet research showed me that I am far from alone in the disintigrated UNI filter club.
I've had the Twin air in for 2 years and it still looks new after 14 kabillion wash/re-oil cycles. I use whatever filter oil is in the cabinet and white lithium grease to seal the rim. Carb stays clean, bike runs perfect, no complaints.