I recently had to decide between an early 2008 MBP and an aluminum MacBook. After weighing all the pros & cons and generally dismissing the early complaints, I decided on the 2.4ghz aluminum MB. I now feel certain that I made the wrong decision.
The aluminum MB has a great design, the trackpad is as smooth as... glass, and it feels like a sturdy machine. Did I mention the design? It's great.
However, the widespread graphics issues that plagued the last gen MBP's have appeared in the new MB's. Scrolling the contents of a window in any application will periodically cause garbled images and text. It remains to be seen how widespread this issue is, but I think it will prove to be at least as common as it was for the MBP's. A look around Apple's support forums will show that the same issue is cropping up in all of the new MB's & MBP's. This is on top of the well-known complaints about the new display: the blacks are definitely washed-out, and the glass is far more reflective than a CRT. It is difficult to work with your back to the window, or in a room with incandescent overhead lighting. If color accuracy is important to your work, you would need to purchase an external monitor.
If I were you, I would sell the old 2.2 MBP (you should be able to get around $1200 for it), and chip in the extra $200-$300 to upgrade to the early 2008 2.5ghz MBP. You get the multitouch trackpad, better processing benchmarks, dedicated graphics, bigger screen, and a firewire port. MacMall has the 2.5ghz model available for under $1500.
You might end up with the same display glitch, but it seems as though that's likely with any Apple laptop at this point. With the early 2008 MBP, at least your machine will have better specs and a bigger screen with an option for matte finish. Dollar for dollar, it's the best deal out there right now.