The whole 'leaving nasties behind' bit is only bad if you don't get it from a reputable source.
And I consider piracy an 'extended demo' 
And its also software manufacturer's only weapon against the pirated stuff.
Heres whats required for me to want a legit copy:
- Useful
- Affordable (Ie, the opposite of photoshop)
- Good support; and from reading the forums here it seems like thats good.
Tho one of the programs (tweak) i'm a little 'ehh' to using since I run a server os rather then 7.