Computer newbies: I just bought an expensive laptop - was it a $2500 mistake?

if you use it, its perfectly reasonable

I think that as long as you get use out of your purchase, then it is justified. You may not use all of the 8gigs of ram or the quad core cpu right now, but a few years down the road, when software will become more intensive, it will become very useful. Adobe software in particular is known to take up quite a bit of resources, so the ram in particular will definitely not go to waste. Don't feel that you spent a mad amount of money either. In perspective, gamers spent up to $8000 building their gaming monsters!! You should be able to get a great usable lifespan out of it. If you only replace our computer every few years, you may even save money as opposed to buying a cheap $500 laptop that you may change every year.
enjoy your new monster laptop!
-Mark H