dalek - No, no problems, per se, though the SLK-900U hangs down quite a bit and makes rather firm contact with one of the capacitors below my CPU socket. The previous Swiftech and a friend's Swiftech have no problems at all with our A7N8X and NF7-S 2.0, respectively.
_tf_ - There is no one answer. On some machines, NvAGP is faster. On other chipsets, AGPGART is faster. On some chipsets, NvAGP is unstable. On other chipsets, NvAGP is the only way to get AGP stabilized.
Use one. Use the other. Take notes, find your own answers, and try to give this answer to anyone else that asks you such an impressively subjective and thus irrelevant question.
Vargr Prime: AMD Opteron 280 *2 | 4096MB Corsair Value reg/ECC | GeForce 7950GX2 | Dual WD Raptor 74GB | Dual Seagate 320GB 7200.10 | Samsung/TSST 18X DVDRW | Chaintech AV-710 | Thermaltake Armor 8000 | PCP&C Turbo-Cool 1KW | Supermicro H8DCE v3.1 | Logitech X-530 5.1 speakers