It's nice to hear someone benefits from your experience!
I just got back from my vacation where I used the bike in different situations and I would like to post some thoughts...
The Sportster is a chameleon of a bike! It performs pretty well both on the road and on the track.
On the road it is a real blessing compared to any other "real mountain bike" because of the geometry and the gearings (48/36/26). You can go pretty fast and pretty comfortable for long rides - I covered a 40 km distance every second day with no problems at all.
On the track, I also find it very potent. I can ride long XC rides and never feel I miss a "real mtb". I always lessen the pressure in the tyres considerably when off-road biking and this works well.
My current tyres prove a great choise wherever you use them, I find the off-road grip excellent on both rough and loose terain (never tried wet though). Only problem that you cannot go any wider on the rear - I don't know if I would, but it's always good to have the option. Current width is 700x40c. No problem with the front.
STill using the Suntour NEX, since my order for that Reba never arrived, and I think this is the most serious upgrade for anyone wishing to use the bike off-road... and the reba SL 29er is the best option taking into account the cost/ performance criterion.
Also...
new photow will be posted soon to show all the new parts.
Keep on trekking!