I got a 'replica' and it's quite fine, just waiting to get it painted. The quality of the material doesn't seem to be any different from a OEM lip spoiler (helped a local put his OEM M3 lip on, sorta need a helping hand to stick it on and be even across the trunk). He spent about $200 shipped, I spend $50 shipped, and I can't tell the difference. He received 3M tape for his spoiler just like mine.
If anything 'I' goofed, and got the coupe lip spoiler instead of the sedan one when I ordered. Which I think worked out for the best (one of those 'aftermarket' goofs), as it is the correct size for my trunk, but I've heard some aftermarket 'sedan' spoilers are 'short' (still have a bit of a gap of 'trunk' on each side of the spoiler).
Some folks have reported losing their lip spoiler at high speeds (E46fanatics speed junkies). The tape should do you fine, but if you're not worried about ever taking it off, a few dots of glue wouldn't hurt. (I'm going to use the tape and a little glue when I apply mine).
OEM vs aftermarket quality is certainly something to keep your eye on. However many aftermarket 'parts' are more viable than OEM and cost alot less, so keep your mind open to the idea, just depends on 'what it is' that you're shopping for.
