There really are no more issues with the GTP over the GT. The only extra piece of equipment is the virtually trouble free blower. Some blowers will require a coupler replacement in it's time, nothing hard to do and can be done in your driveway with simple tools. Then there's the ever wonderful smell of roses when the GTP owners change their S/C oil.
As for is it worth it? Kinda depends on what your plans are. If you want max gains for light modding, then the GTP is the way to go. You'll end up regretting it if you get the GT.
If you have longer term modding plans, the GT may be a good starting spot for something to add a turbo charger to. There are many here who have done plenty to their 3800SE/GT's.
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Bobby
Died 5/1/08, resurrected 5/15/08
ASCD SD hood, 17" Bullitts, Overkill PCM, 3.4" Pulley, NGK TR55IX, K&N 9" cone filter, JimmyC D/P, U-bend removed, Flowmaster 40 series, Hooker big bore tips with resonators, S/B brake lines, drilled/slot rotors, GMPP handling kit, KYB struts, F&R strut supports, HID's, LED's, 2.5" Air Dam, red GTP overlays on custom badges, white rear insert.