Yes, the bus architecture of your computer hardware will limit the xfer rate. But the seek times on SSD are much lower, plus there are no moving parts and it's cool and silent.
You can get these mSATA to 44pin PATA adapters that look like a 2.5" HDD so you can mount them into slots intended for a 2.5" drive, like in a PowerBook G4 or Mac mini G4.
