^ Aye, also keep in mind if you're doing any kind of regimen, eg "I'm going to ride on the trainer for 10 miles", and you're spinning at ludicrous speed on a cheap trainer, you aren't really riding 10 miles. Your wheel may spin 10 miles, but the energy output required to do that on the road is much, much higher.
I find the Kurt to be pretty damn close, especially since it's a "cheap" $350-400 trainer. (it's cycling, remember?) I average around 18-20 on the trainer, and I average 17-18 on the road with climbs, so it's close enough.
This is a higher end trainer:
Indoor Bike Trainer â€“ Wahoo Fitness KICKR Power Trainer
This is a higher-higher end trainer:
Amazon.com : Tacx i-Genius Virtual Reality Trainer : Bike Trainers : Sports & Outdoors