I've used mine with the extension and the pole gets a really good bow in it. It still works quite well in terms of cutting power but it is really unwieldy/out of balance, especially on a ladder. It is a trial and error situation to get the angle right but it does the job.
If you want lighter setup, you can always get the Ego carbon shaft attachments, including extension piece.
Here is a potential deal depending on how you purchase. Max tools, has a "cash back" type sale going on right now. The best % is if you spend $500, get $100 to spend in October. I look at that as $100 savings on $600. However, if you use sales or discounts on your initial order (one code per order), that is where I think it starts looking like deal territory.
It's also likely that if you spend right around $100 on the redemption, that you will get tacked with shipping, and probably won't be able to stack with certain promotions.
Earn up to $100 in MAXCASH when you shop during the promotion, then redeem your code on a qualifying future MaxTool.com purchase
www.maxtool.com