Only the g2m web client works on linux; anything you need the desktop app for (i.e. pretty much anything for which you are the presenter) does not work.
WebEx's Linux support is excellent though.
Google Hangouts works fine under chrome on linux.
As far as hardware, webcam support is generally good. It's now at the point where if you bought a random webcam, there is a better than 50% chance it will just work. That being said, it's much safer to check if others have used it, or to just buy a laptop that has a webcam and ships with linux support (Both Dell and HP have laptops that ship with linux installed). I have a Creative Labs USB webcam that unfortunately has no model number printed on it (I have a long list of things I don't like about built-in webcams).
Sleep has worked on all laptops I've tried in the past decade or so. Hibernate (i.e. suspend to disk) is much more spotty.
Battery life lies somewhere between windows 7 and Mac, though certain applications are particularly bad at draining the battery (powertop can be useful in identifying these).
In general linux on a laptop has gotten way better; in particular networking is much more bearable now that NetworkManager actually works and it's much easier to find laptops with linux supported wifi gear preinstalled.
[edit]
I saw someone mention audio issues; that reminds me. The situation there is more like what networking was like 5-6 years ago. Pulse Audio promises to provide all the basic features people expect from an audio stack), but sometimes crashes, or drains your battery or just causes weird sounds to come out of your speaker. On the other hand, getting ALSA+dmix setup correctly without pulse audio (which is the only real alternative), is fairly arcane, and leaves you without things like per-application volume control (though many linux applications provide their own software-implemented volume control).