Yep, fusion user here too! Got a good deal with the minimum package 100 mins for £10 a month (up to 400 with the hub/openzone).
I only have a couple of gripes, I'd like to see more handsets, especially smartphone/PDA types (there's a HTC smartphone already available, but only for business customers!). And I'd like to either see an end to the 20Mb allowance, or allow me to use the phone to connect to a wi-fi hotspot and use my FON/openzone minutes, not my 20Mb GPRS allowance.
Other than that, I'm saving money too... I used to be on a PAYG phone, pending about £15 a month, I now get a better package for less money, and I use the phone instead of my landline to make free calls during the day (hub phone in the evening).
That said, I don't think it would be such a good deal if I was paying £19 a month... BT need to look at making it a bit more competative, and increasing the range... I heard rumors that this autumn we should be seeing at least 3 new handsets... should have been end of Sept/start Oct... but no sign so far!
C'mon BT... this is a good system, if somewhat misunderstood... improve the range, and price... then improve the marketing.
Cheers
Alun