I have the BT45 on. Well, I've just changed the rear for a Michelin Anakee but still have the BT45 on the front.
I do mostly motorway commutes and got 8k miles from the rear before I changed it, almost worn to the wear indicator (the sirac's I had before gave me 11.5k).

I've not posted a full review yet as I'm still considering the change to the Anakee (as that will effect my view on the BT45) but I'm pretty impressed with them to be honest.

Pretty much any other tyre you get for the Tenere is a block tread of some kind which will all whiteline considerable more than the BT45. The sirac I had was horrible (I replaced it with 3-4mm left and squared off, because of the whitelining) wheras the BT45 only had modest whitelining when completely worn. The dual compound really helps there as it keeps it a bit more rounded as the sides wear quicker (and give excellent grip).

The BT45 benefits over the AM26 in that it's a dual compound tyre, so usual harder centre and very grippy sides, it also has sillica for better wet weather grip. AM26 boasts long life but you can't get that and good grip as easily without the dual compound so there must be a compromise there somewhere (for BT45 it's probaly price). AM26 aparently resists whitelining with it's centre groove, I'd rate the BT45 as excellent there so not much in it there I suspect.

I'm not a massive fan of the looks of the BT45 however (compared to the sirac's or Anakee I now have). The front is fine but with only a narraw 130/80 rear tyre the streamlined bt45 seems a bit girly. AM26 looks marginaly better but probaly much different.

Prices on M&P show about �15-20 more for the BT45's than the AM26's, most of that difference being on the rear tyre of the set. If I was going back to more road tyres next summer I'd probaly go for the BT45 front (grip/handling/[confidence) and try the AM26 rear (cheaper and better looks - I don't really need the handling there).

In short I highly rate the BT45 and suspect you get what you pay for over the AM26 (which I have not tried).