Your experience is not uncommon. Your HD programming should look much better once you get your new tuner. http://tech.yahoo.com/blogs/patterson/578?comment_start=86&comment_count=20
Consider this. Standard def programming varies from about 350 to about 450 lines of resolution, give or take. It is often about 425 lines.
Your new HDTV essentially doubles that (or better!). However, since SD programming is still 425 lines of resolution (for argument's sake), your tuner (TV or cable box or satellite receiver) has to do its best to make up the difference. Some do a better job than others, but a good many are only fair or even poor at it. This results in a soft picture.
Your new HDTV will likely present a picture you appreciate when connected to an HDTV tuner and viewing true HDTV programming. Note that some channels call themselves HD but broadcast very little HDTV content (TBS-HD and A&E-HD come to mind).
Note that not all HDTV's have equally great picture quality, just as all standard def TV's do not. Ever walk into a TV shop years ago and see huge differences in picture quality? You will still see the same in today's Best Buy's and Circuit City's. Not all HDTV's are created equally. I've heard that Samsungs are above average displaying true HD content.