I would have to say that I prefer red or yellow stance, switching between them as the situation demands: If I want speed, then I'll use yellow, if I'm not so worried about speed, I'll go for the higher damage of red.
Generally, when facing blue stance users, I go for yellow (rarely red, depending on their technique of fighting - difficult to explain, but it has to do with whether they dance like loonies or not). Against yellow stance users I prefer Red, but if they are fond of staying in close and keeping up the pressure with constant attacks, I'll switch to yellow for the higher speed again. Against red users, I will often start out with red, land a solid blow or two if possible, then move in with yellow for the kill. Alternatively, I'll use yellow the whole time, ducking in under their slower blows and out again. I prefer yellow for this because of it's greater damage potential and the fact that it is too easy to hammer a blow past blue with red stance. I also have to say that I read a few lightsaber combat guides, which have a number of very useful tips on how to fight. I actually recommend ArtifeX's guide on the Anti-Saberist Code website (don't have the link though, got it from jediknightii.net)
As for "Is lightsaber combat ruined?", the answer is No. It has been changed significantly, to the point where old learned tactics are no longer as useful as they were (if they are even valid anymore), but not ruined. I actually have grown to like the increased blocking in a no force duel, since it makes the fight longer, more interesting and impressive to watch.
The increase in damage/usefulness of the backs**** maneouvers is unfortunate, but I think they did need to do more damage than a normal swing (maybe not as much as they do now though), if used in proper situations or more tactically, rather than running around backwards trying to get a stab in, then they add to the flavour of a combat. One example I'll give from a game I played last night was when a multiperson fight was occuring in the ffa_ns_streets level, and I jumped across from a far away ledge next to an enemy, span round just before I landed into a backswing move which killed him, (without even any backwards movement). If only wish I'd had that game recorded so I could watch it from another point of view. On the other hand, several people I fought insisted on spending quite a lot of time running backwards in my direction trying to backsatb me - that's not fun, that's just silly.
Right, now I've mentioned that I use the backswing, I'll just go put on my abspestos robes so the flames don't hurt.