unless you have work lined up that requires 40ft or more specifically 60ft pole then think twice about buying until the big jobs actually arrive. You are looking at a very expensive purchase which may just gather dust in the shed.
From an operational point of view, any glass fibre pole over 30ft will have an appreciable amount of bend/sway from the thinnest top extension when fully extended and you will find any attempts to pull the brush head away from the glass to rinse/move to next window very painful after even 30 mins use.
I have no idea about 60ft poles but after experiencing the discomfort in cleaning above 30ft and in anticipation of damage to my muscular/skeletal system if I were to use such a pole consistently and long term, I have decided to clean up to a maximum of 30ft.
If you are mainly cleaning 1st floor domestic, then an 18ft (3 x 6ft) is ideal...like waving a lollipop about. Some people on here use a 12ft for the same purpose but I find the extra length allows me to stand away from the window at a shallower angle and wash/rinse more comfortably.
I had a 36ft powerpole but personally found the clamps a bit of a pain when extending and shortening pole and the brush head assembly seemed very top heavy and difficult to manage at the end of the top extension when attempting to move from window to window...that is actually an understatement, I actually couldn`t manage it without feeling my lower back was about to rupture.
If you are just doing residential, get a small3-5ft glass fibre for downstairs and an 18ft glass fibre for tops.
Get a pole with the basic plastic angle joint for the brush head, you do not need a heavy and more expensive alloy gooseneck.
Regarding brush heads, I use Vikan 10inch and have found them to be no problem. I always lift brush off glass when rinsing so have not experienced the problems that other people appeared to have had regarding the vikan brushes holding onto dirt and subsequently contaminating the glass leaving spots.
There is a new brush around called the "salmon" which sounds good...maybe Peter Fogwills.
Anyway...think carefully about what work you do and don`t commit to a big spend just to have the tools in your bag.