I'd rather have it on a 15" HR. I need the express card for esata connections to a scratch disk for video editing. I'm coming from a Late 2008 15" unibody (the only 15" unibody with expresscard) and the resolution was tight for video editing. A 17" will be a great improvement for me but the size for travel is what I will have to get use to.
Have you personally tested the Tempo SATA Pro? I had problems and sent it back using a OWC Elite AL-Pro mini.
I ordered the 17" because I use it to test and use various ExpressCard products including those listed on Sonnet Technology's site:
http://sonnettech.com/product/computercards/index.html#expresscard34cards
It's the only way to add external eSATA interface, or add a second FireWire 800 data channel, or a second Gigabit Ethernet port to the MacBook Pro. It's also useful for broadband modems and flash card reading.
Have you personally tested the Tempo SATA Pro? I had problems and sent it back using a OWC Elite AL-Pro mini.