The Kombi system is very popular, it saves buying a powerhead for each attachment. The downside for the pole pruner is that it is not extend able, you need to add extensions which are not cheap.
Do not try to run the hedge trimmer attachments on the HT101 pole saw, the shaft bearings won't handle the vibration. The new HT131 has an extra bearing that is a much needed improvement.

Thanks canguy. I am considering the new KM130R powerhead. I realize I will have to get the optional shaft extension on the pole pruner, local dealer has for around $55. Are the attachments easy to change?
Clint

Loosen, clamp, remove attachment, install needed attachment, tighten clamp. It takes longer to describe the change over than actually doing it.
Other manufacturers have a secondary latch to add a step but it prevents the attachment from falling off if the clamp vibrates loose. Stihl should look at that.

I have the STIHL KM110R with the Hedge trimmer and the Pruning saw. I also use the extension, which I think is about 37" long, when necessary. I have used them for two years now, and am very satisfied. The 4Mix engine starts easily, and has plenty of power. Charles Ranheim