We use Novogene for all our sequencing, and have never had any problem with them - we've done all sorts - low pass whole genome, RNA-seq, NET-seq, smRNA-seq, iCLIP - granted, they only made the libraries for the standard RNA-seq and smRNA-seq, and other times, they've sequenced libraries we've made.
As for comms/customer service side - when we first started using them, we had a very good rep that covered our area and when ever we needed anything dealing with , we just when through her. Then she moved on, and for a while things weren't so good, we'd go ages without hearing from them, stuff would take a long time and communications seemed difficult. Now we have a good dedicated rep again. Nice guy. Always help. So I think if very much depends on who your rep is an building a personal relationship with them.
As for why it's so cheap - it's been pointed out - they have a lot of very high-throughput sequencers. Your sample will be one of many on a given lane. I also have a suspicion that they handle such a high throughput, that it would make sense for them manufacture their own library kits. You'll note that nowhere on the website does it say whose kits they use. If you ask them to break it down the RNAseq cost into sequencing and library, you'll see that the library prep costs really are very low.