It's ofcourse hard to only rely on reviews and youtube doesn't give much of an impression of the sound. So i'll adress some issues that you might come across there.
Sound: Well, see the topic of this review. Out of the box I always test with Pink Floyd because I've listened to it enough to know what to expect. There is incredible detail from high to low, basses do not get muddled, high mids and treble are clear but not sharp and I might suspect a little forgiving, so the high frequency lever on the back might be something to consider adjusting. But the bass my friends... it's more than you'd expect even from the reviews. I still don't know if it's slightly hyped or it's just that other monitors aren't able to perform and reach that low. It's simply stunning, and not just for hiphop, edm, but even a normal drum kick has a clear thump to it. You will not need a sub anymore. The bass still fits in the overall frequency range in volume, but it's just present in a whole different way. The overall sound with the full bass and non-shrill highs give a nice warm sound, while absolutely remaining a studio monitor that reveals what is in your mix. But, as I often do, I also just want to have a listen, and it will be pure joy to do so.
Volume wise you just don't have to worry. It'll be enough to make your ears bleed while having a smile on your face.
Hiss: Yes, there is a slight hiss, barely audible, and definitely not something that disturbs. My computer makes more noise. I've heared worse on other monitors but if you want absolute quiet in your studio it might annoy you. But any sound and the hiss is just not an issue at all anymore. I suspect earlier versions actually had more hiss but Tannoy fixed it in later models.
The huge sweetspot is definitely true, you can move around and still hear the soundspectrum as it should be. Panning is ofcourse good but I have heared better (mind you, in speakers a lot more expensive). Instruments are still clearly spaced but it's like there's a narrower space. Ofcourse you could just move the speakers a bit further apart if you have the room. (I'm just comparing with my previous set).
Features: I still give it 4/5. Not that there are a lot of features, but the point is that you don't need much adjustment. I could imagine though that some people would want more settings to adjust to the room, but that can also be helped with acoustic treatment or arc, or, if you're a happy amateur like me, it won't be much of an issue.
Buildquality is as it should be, heavy little monsters with a good finish and overal good looks. In the reviews I never got why anyone would go for the 502 or 402 "to save room". It's not like they are huge and with a normal desk: I have a 140cm desk, 27 inch screen and they are standing on either side and i still have room to spare. I would so recommend laying down the extra cash to get the sound of the 802.
Conlusion: If you don't have the possibilty to go out and listen for youself, take a chance. For anyone on a bit of a budget this will be one of the best you can get. If you have the possibility then put any pair up against them in a music store and be surprised.