Paul McGuinness is the person that cares about #1. But it's his job to do that.
ATYCLB debuted at #3 - never reached #1. Yet its first week sales were around 428,000, which was greater than AB, "Zooropa" and "Pop"! ATYCLB produced the best first week sales for U2 in the SoundScan era, yet failed to get to #1. In contrast, "Pop" did reach #1 - but as we all know, it had a pretty quick descent from the charts. ATYCLB spent nearly 2 years in the Top 200 on the Billboard charts - "Pop" spent something like 4 months! So a #1 debut (or ranking) doesn't always mean a hit album.
What sells albums is how long HTDAAB can linger in the upper echelons of the Top 100. During the holidays, albums sell by the boatloads. U2 is wise to release an album at that time - it's worked well for them so many times in the past (R&H, AB, ATYCLB and both "Best Of" albums). HTDAAB may not stay in the Top 10 long. ATYCLB was only there for 2 weeks (it later hit a third week in the Top 10 after it won 4 Grammy awards). But the strong holiday sales will keep it afloat for quite some time. If you look in the "Peeling Off the Dollar Bills" forum, Doctor Who and Sting2 have quite a few posts about charts and sales - and one can see how the two don't always relate. During Christmas week, sometimes the entire Top 50 sells over 90,000 copies - and that's not including huge catalog sales!
So don't be worried about #1. Rather, keep a watchful eye on how long HTDAAB lingers in the Top 100 - that's what really determines how successful an album is.