I'm in this situation myself. Around New Years' My mid-2007 MacBook no longer charges its battery, and according to the Apple Geniuses it requires a costly logic board repair. Instead of investing hundreds of dollars in what is already a 2.5-year-old computer, I decided to get a new one. I was disappointed to discover that the base 13" MBP had the same processor (only 100MHz more, but with 1MB less cache), same RAM, same display resolution, etc as my current MacBook, and is only $400 less than what I paid 2.5 years ago. However, since Apple had scheduled a media event for the 27th of January, and since I figured there was a good chance of an update during the event I decided to wait.
Now that the event has come and gone without a word on the MBP lineup I've started to question my need for a Mac. I've already installed Ubuntu on a partition of my current MacBook to see if it can meet my needs, and I've started to question my investment in my Apple infrastructure (Power Mac G4 server, iPhone, Apple TV, Airport Extreme, etc) and look at other options (I've had my eye on the Nexus One). Though I'll still likely purchase the MBP update, assuming they can get it out by the end of the month, it may very well be the last Apple product I purchase for a while, if ever.
Now that the event has come and gone without a word on the MBP lineup I've started to question my need for a Mac. I've already installed Ubuntu on a partition of my current MacBook to see if it can meet my needs, and I've started to question my investment in my Apple infrastructure (Power Mac G4 server, iPhone, Apple TV, Airport Extreme, etc) and look at other options (I've had my eye on the Nexus One). Though I'll still likely purchase the MBP update, assuming they can get it out by the end of the month, it may very well be the last Apple product I purchase for a while, if ever.