Changed to a C4 and like it!
I replaced a REALLY big Channel Master 3671 antenna with a Clearstream C4 antenna a couple of weeks ago and I can highly recommend the Clearstream - about 10% of the size with much better preformance. Being 60 miles from the LA transmitters with sizeable hills in the way I also need a good pre-amp and signal booster and I used a Channel Master 7777 pre-amp on both units with good results.
The C4 is specially designed to pick up the channel 7 thru 69 range of digital signals which will be the survivors this coming February. Be forwarned that it does a poor job of picking up any of the old analog channels. With the new C4 I pick up all the major channels with the exception of KCOP13 - which we seldom watch anyway. The Channel master did not pick up 3 of the 7 major channels and the reception came and went with the weather conditions.
A word of caution - when you use the antenna web sites be forwarned that they sometimes give misleading information. Accoding to tvfool I would need a 300 foot antenna to get most LA stations but I do just fine with a little under 30 feet from ground level. Start experimenting with what your ideal setup would be then work your way up from there - like better antenna, better signal boster, higher mast, etc.
Concerning choosing and buying an antenna - use the web to research and choose the make and model you want, then google it. All I get when I talk to Radio Shack, Circuit City or Best Buy salesmen are wrinkled eyebrows and reference to the Direct TV display - so don't depend on them for expertise. Do your research, look for writeups and references, then find a good online vendor with a good return policy to buy it from. If you can find it on Amazon check out the recommendations that most items carry to find complaints and recommendations and if you buy it through them their listed vendors usually have a good policy of accepting returns. If you are looking for RG6 coax, splitters, any type of audio/video equipment - check out Monoprice dot com. You might wait a couple of days to get your parts, but you can not beat the prices. When I bought my C4 through Amazon on Wednesday I ordered some supplies from Monoprice on Friday and had everything delivered by Monday.
Good luck on whatever you decide on - can't beat free HD TV!