I have been dealing with this issue for a few years now, having 2 MTBers in the family for whom I supply most of the $$ for parts and upgrades.
If you like the feel of the bike you have, upgrade it. You will learn, which will inevitably cut down on bike shop repairs, and you will end up with what you want - plus, upgrading is a little $$ here, a lot of $$ there, but all in bits and pieces, instead of one huge outlay for a new bike - and you may not like the stock components. If you're serious about your bike, upgrade until you need a new frame, and then get a new frame & transfer your parts! (see the "help - I'm just a mom" thread)