I'm currently researching a multi-city itinerary. I checked ITA and it came out at 1054GBP. I checked UA in stealth mode and it priced at 1014GBP. I logged in and it priced at 954GBP. I then switched to USD and it came out (given current exchange rates) at nearer the ITA level.

I'm not sure what I learn from this, but clearly UA is not charging me more for logging in and clearly ITA is not finding the lower fares which UA is offering (lower is a relative term here as the fares are a good 30+% higher than last year).