Yes, I owned a 996GT3 for over 3 years and 30k+ miles. Modded pretty much everything on it during that time courtesy of Manthey and it was a razor sharp track-focussed scalpel when I sold it earlier this year. Out went the GT3, in came the CSL.
I think it depends on what you want to do with the car. The 6Gt3 is a brilliant tool. But I think it is very hard to fall in love with, in the same way the CSL rewards you instantly. The GT3 is all about precision driving, eeking out the fastest and smoothest lines, perfecting your braking approaching the apex, and modulating the throttle at and through the apex. It rewards you in 0.01s against the clock. The GT3 also gives you the sense of occasion on road trips and bragging rights in the paddock... something you never really get with the CSL. If you are chasing 10/10ths on track, relish the attention on the road and in the paddock, then the GT3 is tops (apart from going the Lambo/Fezza route)
But the CSL is, by far, the most fun car I've ever owned! For one, it's understated. SG/SB is about as exciting the colours get, and for most on the road, it's just another 3-series. Flying undercover, imho, is a good thing - especially in this market. The CSL rewards you instantly on track - you can pitch is sideways, in the dry, in the wet, and get away with it. It is easy to drive at 9/10ths (easier than the GT3), and it is the quicker car A-B in real world road conditions. In short, the CSL is an absolute HOOLIGAN!
On track, the GT3 at the limit is tricky - it will teach you how to drive again, steering from the rear, and using the mechanical grip/aero to your advantage. Underestimate it, or overestimate your abilities, and it will bite. Hard and fast.
Depending on how deep your pockets are, you will either find tracking 45k worth of GT3 painless or poor VFM compared to 25-30k of CSL. Especially when the CSL is good enough to give the GT3 a proper dogfight on most circuits (except on power circuits like Spa/Silverstone and if the circuit is clear). At the 'Ring, there is nothing in it except for driver ability. The CSL laps as quickly in pro hands as does the GT3.
On the road, for normal hooning around, the CSL is the better car imho. Add in occasional passengers/urban use etc, and it's a no brainer.
I don't miss the social attention of the GT3... but that's just me. Both cars are equally special - there are touches of the CSL that make it feel very very special. Hold out for the CSL imho