The sl's are very light, snappy and precise. The skis immediately hook-up when put on edge and grip like monsters. I've pushed them as hard as I can in the gates and on the groomers and they NEVER let go on me. The only time I will loose an edge is if the snow breaks away under foot. The skis are capable of dealing with whatever you can dish out.
When I got the sl's they had a thick titanium plate on them and I really did not like the ski. It was way too stiff and unforgiving. I've since put a 16mm WC Vist plate on which I chopped in half. It skis flawlessly now and i have no complaints. The retail plate is also top-notch and all of the racers who I have spoken with love the performance of the whole package. I'm using race-stock Marker bindings with titanium shims to bring the lift to 55mm on these skis.
The GS also has great edge grip and is very stable at speed. The Fischer is not quite as damp as some other gs skis which may or may not appeal to you. I use this ski for tight GS sets because I find it quite a bit easier to bend than my Elan GSX's. I don't think that you will too many weaknesses with Fischers race line this year. I have a Vist plate and Comp 1400 EPS's on this setup.
If you can get a good price on them then go for it. The sl is nearly as good (IMO) as the Elan SLXT. Nothing else off the shelf can compete with those two skis. You may prefer a different "feel" for your GS skis than the Fischer offers, but there is no denying the products outstanding performance.
I'll hopefully be going to Boyne next week for the dealers demo show and will get to try all of next years equipment. I'll post my impressions of the race skis when I get a chance.
I've already been on next years Rossi and Dynastar 10 race skis and was left totally underwhelmed... just more of the same wimpy cap skis that they have been pushing.