bought an '04 Iguana (disk) for my son's Fiance. Gotta say it looks and rides nice!
I'd say well worth keepin and doin upgrades. Fork isn;t half bad either.
Frame seems nice, light enough and solid
Nice thing about 'upgrades' is you get to put on exactly what you like, and do it piecemeal.
A chance to experiment and 'try', ebay what you don't particularly like.
The stock wheels are pretty nice, at least on the '04.
Overall, a very nice ridin HT, even 'stock'.
Downside is (unless yo keep the old stuff to put on later) the upgrades won;t give you much more resell value if you decide to sell later - it's still seen as an Iguana.
Like another said, I;d get another wheelset to use (keep the original set), ride the bike as is, replacing stuff as needed and when you have a really good idea of what you'd like next, then 'build' it back to stock and CL.
The Iguana offers a lot of hard ridin as is, as long as you have a wheelset which can take some hard treatment.
I'm no egg-spurt, but I used that 'plan' with my Trek and glad I waited and rode the piss out of it before lookin for another bike. Found I really like the 'longer' TT of the older Treks (like GFs) and not the newer more upright ergos of a lot of the new bikes. I prolly would have made an expensive mistake (for me) if I had decided to get another bike, sooner.