Mavericks, Mavericks, Mavericks! Let buggymite mature a bit more... (or just let it be, 10.9 is great for an 2008 model, no need for anything newer really)
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btw, my MBP17 from 2009 is upgraded with an crucial M4 256 GB SSD and 8 GB crucial RAM. Trim enabled, works great!
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...and runs 10.9.5!