First off, I don't work for Seidio, no financial interest, yada yada yada...
I have the Seidio holster for the "naked" Curve (I think it is called rubberized holster) and I am very happy with it. The clip holds the Blackberry very securely, yet you can still take it out of the holster with one hand. It attaches to my belt very securely and has nice solid "notches" when you swivel it. If I ever lost it, I would replace it immediately.
I also have the Seidio screen protector and again I am very happy with this item. My wife installed it on her BB Curve and after I saw how good it looked, I let her install mine as well. No bubbles, quick and easy installation (based on no complaints from my wife), no problems with it coming off. I honestly have to look at it very closely to see that it is on my Blackberry. I don't think a casual observer would ever see it.
I didn't actually want a screen protector originally since I was concerned about it making the screen look less good in some way, but when I ordered the holster I saw the screen protector was $6 and claimed to be removeable without leaving residue, so I figured at worst I'd be out six bucks. Turned out to be a great item and I would highly recommend it.