Web connection produces very simple html and uses very little html form magic or the like, so I'd be surprised if you face any problems. The Web connection apps we've done have come from some netscape/mosaic legacy to firefox and IE 6 and 7 without any problems. The apps still look as poorly designed as ever
Do you use any styling in addition to bare web connection parts? how is that stuff generated?
Do you have a machine available on which you can simply try? As Taylor pointed out, MS has put a lot of effort in making IE8 both standards conform as well as confroming to its own legacy...