Thought I'd chime in. I really liked the T-Mobile leather holster that I used with my Pearl, but the one for the Curve seemed too big. I looked at the Blackberry OEM one, but didn't like the plastic/bulky clip. So for the past few months I've been using a cheapy eBay leather case (from the recommendation of someone; perhaps in this thread!). It's "ok", but the leather was really cheap and I was always looking for something else.
Today I received the Speck Holster-Pro. Bought it off eBay for $17 shipped. Turns out it's a highly discounted item at many online retailers, so you may even be able to find it cheaper with some hunting.
I wanted something really slim and this looked like it would fit the bill. The construction is top-notch and the clip rotates which is a bonus. At first, I was shocked at how tight the holster gripped the Curve. It was basically useless, requiring the firm grip of two hands to wrench it out of the holster. What's the point of that?! I was so irked I actually wrote Speck and ranted to them about it.
Well, since I had already bought it, I knew what I had to do. I grabbed some pliers and basically bent the "ears" of the holster here and there, breaking it in so to speak and easing up on the preformed curves a bit. I used a folded piece or cardboard to protect the leather from showing any marks. I also squashed the bend in the belt clip just a bit to make it hold even tighter.
Now, the Curve slides in and out easily, yet still holds firmly. It has the exact feel I was looking for. My preference is to carry it face-in, but the fit is not as good as it is when facing out, which I believe is the intended position. I can even shake it wildly and it won't fall out. But since the grip is better when facing out, I think I'll put it into that position when carrying the Curve sideways, which is what i do sometimes if I want to "hide" the holster from view. Otherwise, it's face-in and on my front pocket.
Here's a pic. See how nice and slim it is? It won't accommodate my rubber skin anymore, but that's ok. As long as it's always back in the holster, I don't see it getting too banged up. Oh, and it has a sleep magnet, too, which works face-in or out!