The latest version of Skype for mobile devices including Windows Mobile is the beta version - 2.5 which is supposed to be more stable and also look more like its cousin which runs on your PC or Mac. I tried the beta just now and was impressed with sound quality on my HTC XV6800 phone running on Verizon EVDO.
I did notice the interface did look much more like a PC and while the sound quality was good, I couldn't figure out why the call seemed to default to my speakerphone with no way for me to stop it from doing so. I should also mention that I tried the call with echo cancellation turned off and I noticed there was no echo on the particular call I made.
This is the default setting and if you change it, you will likely slow the device and chew up processing horsepower. Overall this beta is impressive and I hope the next Skype app I download is for the iPhone.