I don`t know about FS Global 2008 but I can give you a fair bit of info on Traffic, now fully FSX compatible, not made for Vista but works perfectly fine on it.  Good models, much improved from the poor graphics of the 2004 version.  A fresh download of improved textures available after purchase.  Works straight out of the box and gives much more third party traffic availability + the necesssary increased parking at major airports.  Due to the changes its advisable to download the jetways patch after install also, this addresses lack of jetways and some minor stuff like taxi way signs on the runways at some airports.  All in all, well supported indeed.  Many Ultimate Traffic users have stopped using that product and moved to this one.  FPS not unduly affected if at all in XP or Vista.  35% traffic (the level I use) is probably in excess of 50% at default FSX traffic, so adjust accordingly.  Obviously you have more aircraft, so the percentages are artificially higher with this.  You need a balance but not so much that the comms is chocker with chat from other aircraft.  I knocked out the TNG traffic (touch and go) on mine because they drove me round the bend, did it manually.

Pricing:

The site you mentioned has the product out of stock at the moment, was when I checked.  Just Flight has it in stock as a DVD or a download, same price either way and about the same price as the other site.  If you join Just Flight as a member (free and quick to do) you instantly get 500 points toward future purchases.  You can then sign in and knock the points off this purchase, then be awarded 200 extra points for buying it too.  I bought mine in the shops but heres an example in UKP.

If I wanted to buy it at £19.99 and got the 500 points I would pay £14.99, then get £2 off a future purchase too, making the real cost £12.99......nice one!  Mondays are currently half price on selected products too, only one per day.  Knocking off the points may be subject to an allowance per item.  I bought a £29.99 item and got £5 off, it may be pro rata on £19.99 and not sure how it works in dollars either.  Just Flight also has a forum with valued info in there and screenshots too.

Should be enough info for you to make an informed decision, have fun and enjoy.....

Reider