USB3.0, meet laptop hard drive (Q's about speed)

[Comp_passion]

I just bought myself a fancy new Ultrabook with all superspeed USB3.0 connections, but the built in hard drive unfortunately only came with a 320gb hybrid hard drive (Zenbook UX32A-DB31). I dug out the HDD from an HP laptop I had sitting and found myself with a 400gb 5400rpm Toshiba MK4058GSX, but it's only SATA3. I have a USB3.0 enclosure to put it in, so I know the only bottleneck now (if there is any) will be the hard drive itself. I know the 3.0Gbps that SATA3 technology claims is only theoretical so what should I be looking at as far as the limits of this little laptop hard drive. Or for a more general question, how well does USB3.0 play with 5400rpm hard drives? Any help or advice is much appreciated, thanks! BTW first post, so hello to everyone

 

[Cons29]

it will be slower (compared to 7200rpm). but then again even 7200 will not even max out sata2 speeds. only ssd's can do that