capacitive = no stylus = no painting

Wait - are you promoting the touchscreen based on using a stylus? Or fingers?

Does the N900 have a dedicated stylus holder or is it normally used with just your hands?

stylus slips down bottom of n900 brilliant device

i use the stylus a lot but it's equally as good with fingers

I normally just use my finger nails, and it works perfectly. But yes, there's a dedicated stylus holder(and stylus is included).

the resistive screen is only to habituate. you need more pressure than on an capacitive but after a few days of usage that should be no problem.

But then, the N900 screen needs much less pressure than any other resistive screen I've used.

I'd keep the WP7 device for calls and get a cheap secondhand N900 for a tablet/netbook/mediaplayer if I were you. Phone functions are not the strong point of this device...
As for the screen it is superb. It is really sensitive and readable, it has a transflective layer like the PixelQI screen in the Notion Ink Adam tablet, so it is readable in strong light, in fact it is readable even with no backlight at all in a well-lit area (also turns b&w). It has its shortcomings thou. Many users experience some light spots on the right side of the screen, always the same place. It also does not support multi touch, but as I said it does not affect its usability, but many games require multi touch, you has to play these with keyboard. The Maemo linux is an amazing mobile OS with great potential, but it has shortcomings you would never expect (lack of portrait mode for one). If you want an interesting device, you are right to choose the N900, it can do things no other device ever can dream of, if you are willing to learn how to do it.

N900 touch screen is indeed very good, but it is resistive, ie pressure sensitive. As other have stated above, you need to apply slightly more pressure than on a capacitive, and it works better with nails than with a large surface (whole finger). It is really a matter of habit. As I have used resistive screens for 3 years, I feal more akward now on a capacitive one.

For the N900 in general, well it truly is the device I have enjoyed the most in my short life, but on the other hand I wouldn't advise it to any one in my familly (or any non geeky friend). In my opinion:
Pro:
- really feel free
- no 100,000 apps, just the 1000 you will ever need, plus the web.
- allways something to work on
Con:
- not really a gaming device.
- 18 months old, even if high end.
- allways something to work on

See it like moving from an all-inclusive resort holyday to a lonely planet trip with the same budget.