I’m actually not impressed with ubuntu on my laptop either. It’s fine on my work desktop, and on my home desktop, but very unstable on my laptop. Although I don’t know whether it’s a specific issue with ubuntu, or something else, probably the latter.
You may want to try another distro, I’ve heard Xubuntu runs better.
Xubuntu
There’s hundreds of distro’s out there, some targeted at giving you a very lightweight and fast base installation. They may be worth a look, but they probably won’t have the popularity of ubuntu, hence community support may not be as good.
Most distro’s are pretty similar under the hood anyway, so the biggest difference is what window manager your using, and whether you have all the bells and whistles enabled. Try disabling if you do.
Make sure you have the best drivers for your wireless card – just google around see if anyone else has had any similar problems. Network speed should be as good if not better than in windows.