I have a late '08 MBP and just recently upgraded to 8GB of RAM and put in a new 1TB HD, along with installing Mavericks. I am very pleased with the performance after all of these years and will wait at least another upgrade cycle before getting a new MBP.
Same here. I'll wait because I don't think the pricing of the current line up justifies the specs. 1330 for the base model with 4GB memory is a joke and I'm quite confident they will discontinue the 4GB model in the next cycle.
Then, I will buy the 16GB model for the sake of making it future-proof. I bought my unibody base model in 2008 with 2 x 1GB, upgraded it to 2 x 2GB and eventually to 2 x 4GB. I'm not going to buy a 2 x 4GB model now, not being able to upgrade later and instead be forced to buy a new machine within 2-3 years - I want to keep it for at least 4-5 years.
I also put an optical bay in my machine and replaced the 160GB hard drive with a 256GB Samsung SSD.
Apart from the fans spinning up relatively quickly, I have no complaints about the performance of this amazing machine - even after 5 years!