I’ve only ran ubuntu on my desktop and in VMs in the past so I can’t comment on netbook speed.
I only started getting back into Linux at 12.10
I played around with Linux before then but not enough to know true speed comparisons with 12.04 or before.
I have an SSD in my desktop and 12.10 was rather snappy to begin with but would lag from time to time depending on what I was trying to open. 13.04 seems much quicker in those areas. Software Sources from within the Software Center still takes forever to open though. Probably because it’s scanning the hardware of the pc as it opens.
The dash has seen big performance increases as well!