I use a Lenovo X220 with an SSD and a 15" MBP (also with an SSD). They're both fantastic machines. The Lenovo lets me use Linux with pretty much perfect compatibility and has the best keyboard I've ever used. The MPB similarly has the best trackpad I've encountered. The main unexpected advantage of using OS X has been the presence of readline-style keyboard shortcuts at an OS mediated level (in any text field). Once you get used to that, using any other OS for incidental typing (in search fields or forms) feels slow.