well... all netbooks are modern enough to have built in wifi, so there is no need to add on an external wifi adapter.
Also, yes, netbooks are slow. It is their nature to be 'bare minimum' laptops that are good for browsing the web... and nothing more. If you run a tight ship, only installing absolutely nessessary software, making sure that your registry is clean, keeping tabs on your startup programs in msconfig, etc. Then you can get a fair amount of power from a netbook. I use mine all of the time to do audio recording with no problems, and after upgrading to 2GB of Ram it really helped speed things up. But it is equivilant in speed to an 8 year old pentium 4 (but instead of 140W it takes a mere 4-8W), so yes, they are quite slow even under the best of conditions.
Netbook is netbook, not a laptop, for slow performance issues usually two ways to fix: upgrade hardware or clean the system http://www.speedup-netbook.com/ If still you can't put up with it, go get a "real computer".