Got my /B card yesterday from PowerMax. I swore to myself when I ordered it that I would use it only as a last resort if drivers for the ExpressCard solutions never saw the light of day, but my resolve broke and I installed it this morning. It only took about 30 minutes. I don't have an 'n' station yet, but I've seen no degradation in signal strength with my 'g' network. The 'n' enabler came on the included disc and it installed without the need to use something like Pacifist. I verified using Network Utility that 'n' is indeed enabled.
As for the yellow tape on the edge of the stock card, its sole purpose appears to be to restrain the little cable that runs alongside the card. I just unstuck it from the old card and stuck it down under the card slot, making sure that the cable was out of the way of the card, so if I need to put the old card back in for AppleCare service, I can simply unstick it from where it is and stick it back on the card.
I'm now eager to get a new Airport Extreme base station and run a dual-band network. My 'n' network will be used initially to allow my MBP to communicate with the tethered dual 1 GHz PowerMac G4 that I use as a server.