Fat Bastard Burrito - NEX-5N & Rollei 50mm f1.8 HFT Planar. Click for larger.
I see this Rollei 50mm f1.8 HFT Planar as a sister lens of the more popular Contax Carl Zeiss 50mm f1.7 Planar. I think it deserves better than what most people give it credits for. It's sharp, has got nice colours like the Zeiss. Oh wait, they are both Zeiss lenses! The Rollei Planar is a Zeiss design licensed to Rollei, just like Contax lenses were licensed by Zeiss, so there is no secret that pictures from the Rollei 50mm f1.8 Planar show traits of Zeiss lenses.
The reason the Contax 50mm f1.7 Planar is more popular is due the mount. It can be used with Canon DSLRs via adapter where the Rollei QBM mount is difficult to be made focused to infinity on the Canon. With the popularity of the EVIL cameras, this is no longer a problem. Both mounts will work fine on all the EVIL cameras. If you want to try a Zeiss lens, buy the Rollei 50mm f1.8 Planar. It's much cheaper than the Contax 50mm f1.7, and they are equality good lenses. You will not regret it.