I'm the same as you Daz Auto, really (in an ideal world) would like to get in a FL GTI, but then looked out at my car (which isn't even a year old yet) and thought, even without the fancy LED headlights and new LED rears, the current car still looks the business. Also, whilst the LED units are probably very trick, the Xenon's on my current car are still very good.
Then to the interior. I really like the look of the Active info display (drove a new Tiguan with one), and it's really quite nice and a good use of the space available ahead of the driver. Also, whilst I've no doubts the new discover Nav Pro III in the FL cars which have some additional cool features over my MIB II Nav Pro, (aside from the bigger screen), my Nav unit has been great and when I sat in the sales Managers new FL "R" at my local dealer, the huge 9" screen and gloss black surround was a massive fingerprint magnet and everywhere was absolutely covered with fingerprints.
So for me, currently what it boils down to is about a second faster 0-60 (I'm not really a traffic light grand-Prix person), for the GTI over the GTD (top speed is academic), and maybe a little quicker 30-50 and 50-70, but in itself the GTD isn't exactly slow and seems fast enough. I'd also be losing around 10(ish) MPG average over the GTD economy wise around town to 15-20ish on a run (overall then no biggie). No, for me the real killer is to get out of my 10 month old GTD and get a FL GTI with similar spec, for around the same payments per month as I'm currently paying would cost me around £6k in deposit fees. That's an awful lot for a car that is 80-90% the same as my current car. Don't get me wrong, if I had the money to throw at it, I'd probably jump, as I think the new GTI's with the optional Bresica alloys and the other updated tweaks looks the business.
Unfortunately with the wife being a bank manager, that isn't really an option at present
As such, like you I've decided for the time being (say around the next 18 months or so) to put up with my outdated last generation, oily, noisy and socially and politically unacceptable banger, with it's outdated (so yesterday) lights and clockwork gauges and will consider either a FL or a MK8 (if announced in the next 1-2 years or so) at that time.
The one thing I've learned, is that there will always be a newer model with better tech, different looks and perhaps more efficient engines with better performance just after you have splashed a large amount of cash down on a new car. Chasing the newest and greatest is a fools game.
In any case, the old girl doesn't look too bad does she ?