I just bought a pair of them yesterday after going out intending to buy the S5s. I'm a regular at the Music Store where I went and the staff there made me excellent offers on both the S5s and S8s (AUD$595 and AUD$895 respectively). It would be fair to mention however that the manager there really wanted the salesperson to get me to buy a pair of Roland DS-5s over either of the Tapco's.
I've had trouble finding reviews also, but from what I've seen the Tapco S8s review very differently to the S5s, and might I add not as favourably. That being said when we I tested these monitors on a wide range of reference material (including some of my own 'mixed on PC speaker' recordings) I was extremely impressed.
On songs I was used to hearing on the radio a whole new dimension was revealed, nuances and subteties that I'd never heard before were coming out. On my own early recordings I was anticipating hearing weaknesses and interference, and this is exactly what happened. My mixes sounded entirely different to the computer speakers, HiFi's and car stereo's they'd been played on previously. Frankly, I'm glad that we decided to start recording again as these tracks were originally geared for release (the monitor purchase was something we saw as a necessity before we began tracking again).
I remember reading somewhere on another forum that a particular music store took the S8s out of their listening room because they sounded too 'Hifi'. I didn't have any opportunity to A/B them since in my town there really is only one music store that deals in recording equipment. All I know is they sounds good, they are very revealing of nuances in the pro recordings I've tested them on as well as my own, they give a very good stereo image, and they just sound GOOD.
Final disclaimer: These are my first pair of monitors. Part of the reason I rushed into the purchase, apart from time constraints before we started tracking again, was because I do eventually intend to replace these.
I was blown away by the sounds of these units, but then I'm used to listening to things on computers / home theatres / cars stereos. If I had the opportunity to compare them with more makes and models I absolutely would have, but I was very impressed with them on their own.
If you have a store with a pair nearby go have a listen and make up your own mind. I don't think monitors are something you should just order from MF or Sweetwater blindly (or deafly?).