My observations are that UA.com really has improved the last two years and the ".bomb" reputation on this forum comes now mostly from the inability to handle complicated itns instead of it actually performing poorly on routine functions (and the level of the routine functions that the site can handle has risen).
1) UA.com has definitely improved in the past few years. Additions like seat selection, searching for upgrade-qualified fares, and searching for cheap fares +/- a few days are very welcome improvements.
2) Yes, I'd like to see UA.com handle some of the more complicated requests I throw at it, but what still really bugs me is that the basic stuff still doesn't work that well. Random errors where certain booked itineraries won't display, searches for F/C tickets that fail because your origin or destination is served by only single-cabin planes, upgradeable fare searches the return non-upgradeable fares, etc., are all significant annoyances to me. Add to that the slightly complicated things that, IMO, should work, such as being able to book upgradeable fares even when the last leg isn't served by UA metal (e.g. DEN-FLR on an H fare).
Overall, I think UA's site has improved from "poor" to "acceptable" in the past few years, at least when compared to airlines' web sites overall. It still has a long way to go, but if they could just improve the reliability (i.e. availability and ability to make the existing functionality work well), I think they could have a pretty good site without adding much in the way of new features.
The ability to authorize award travel is a biggie, though, and if they were looking to add new features, that would be near the top of my list of realistic requests. (I'd like to be able to specify fare class on each leg of a trip, too, but that's probably useful to a much smaller population overall.)