If you're looking for a decent iPhone 4 case i'd advise you to stay away from any sort of ultra-thin hard shell cases including the Switcheasy nude. Here's why:
a) They're too thin and the hard plastic material doesn't offer any useful drop protection at all. So you can never be sure your phone's going to hold against serious drops/bumps etc. Plus most of them don't have any sort of "lip" on the front of iPhone and thus no protection at all in case your phone lands on its face.
b) They actually aggravate the chances of scratches appearing on your iPhone. Dust often finds a way between the case and the phone and causes scratches to appear on the surface.
c) The material is prone to smudges and scratches on the outside as well and due to their very nature they tend to be slippery and the chances that you might drop the phone actually increase.
So lets see, they spoil the aesthetics, don't provide any sort of reliable drop protection, aggravate the chances of scratching..well, what are they good for then? Nothing, i'd say. You might as well go without a case.
Then there are another type of cases made from soft silicone material. They're cheap, some of them are bulky offer moderate to good protection but most of them look just downright obnoxious. The color/design choices available are hideous. And because they're purely made of soft silicone they're dust/lint magnets. So unless you don't care for aesthetics at all, just ignore any cases with mention of "soft silicone" in their description.
Now there are only a few good quality cases that offer some decent drop protection without adding much bulk. One of them i'd recommend you look into is the Speck Pixelskin HD. Made from a TPU derivative, it has a great build quality, doesn't add much bulk while providing decent drop protection. One of the few cases with overwhelmingly positive reviews.
Another good case is Incipio NGP, made from TPU material as well. Offers moderate drop protection and doesn't suffer from any build quality issues including the dreaded flash issue which a lot of iPhone 4 cases suffer from.
Then there's Speck Candyshell. Adds a bit more bulk than the Pixelskin HD but provides the best drop protection. Great build quality. Very reliable.
If you want the ultimate drop protection you can get the Ottorbox cases but they suck in terms of aesthetics and add way too much bulk IMHO.
Also, you might want to consider this Suede Jacket from Waterfield Designs. Pretty popular with iPhone 4 users.
SFBags - WaterField Designs - iPhone Suede Jacket - iPhone Sleeve - iPhone Bumper - TSA Checkpoint Friendly
To learn more have a look at this nicely done iPhone 4 September case round-up video here:
YouTube - iPhone 4 Case Round Up - Sept 2010 Edition