I got my iPhone 4 about 6 days ago and like the post author I had some specific criteria...
1) slim enough case that I could use it in a pocket style (like the old Blackberry pouch that the Curve came with) pouch... for when I use a jeans or shorts pocket etc... or in a belt clip style holster for when I am in more dress up situations...
3) Slim enough case to allow the iPhone to sit in my BOSE clock/radio with IPhone/IPod dock built in on the top (kind of like the original post author's requirements)
3) CLEAR (because the iPhone 4 is such a stunning look/feel/design why cover it up when its not in a holster/pouch???)
4) would then fit inside a top loading slide in pocket style case (as I mentioned above)
5) Oh and yes, needed to actually FIND a top loading pocket style case...
So, here was the verdict: I spent 6 days straight looking for and trying (buying and returning in many cases) the right combo for me... It may not be the right combo for you, but I have found a set of items that I am ridiculously satisfied with and quite excited about! The trick is doing a bit of mix and match!
1) The case: I ended up with the SwitchEasy NUDE (clear) case for iPhone4. Its 1 mm thick (so very very thin) super strong polycarbonate. Its got all the perfect cutouts for the volume buttons etc etc... AND even comes with form fitting plugs for the earphone jack (which I never use) and the dock connection port at the bottom ... both of which are places dust and lint can end up very easily. It is clear, so its shows off the design of the phone quite nicely. It also comes with EXTRA cutout plugs and 2 x screen protectors in case you need extras!!!
2) The pocket: I ended up with an INCIPIO pocket designed for the iPhone 3GS. The funny part is, the iPhone 4 with the SwitchEasy NUDE shell case fits BEAUTIFULLY into the Incipio pocket. The Incipio pocket is leather, has an ingenious little hidden tab a the back that even helps you "eject" your phone for an easy pull-out when its ringing etc.
3) The holster: For when I dress up...(but not wearing a suit... because if I'm in a suit the pocket is still the best!! - yes, I needed to add that LOL) I ended up with a lateral flap over style belt clip leather holster that is actually **gulp** designed for the Blackberry Storm. However, with the SwitchEasy nude shell case, the iPhone4 fits amazingly well and very securely... with easy access to grab it and pull it out of the holster.
All in all I find this combo works perfectly for my needs... if anyone wants pics let me know and I will post them.