My own experience (having purchased and still using one grill)...
Skip the side cookers. Unless you plan to actually cook five or six things at a time on the grill (and manage the whole process), they won't come into play. I have never seen anyone who has them use them.
Avoid the neat little window that lets you see what's cooking. If you want to see, you'll open the top anyway, and it's an engineering weak spot in the design. What happens when the little pane of glass breaks? It's not like you can run down to your local convenience store to pick up another one
Do get one with readily available replacement parts. Seriously. Last week, I replaced the burner assembly on this one for the fourth or fifth time. The cooking grill itself, the burner, the lighting mechanism... they all will age, and rather ungracefully. It's amazing how metal can corrode, even when it's not directly exposed to the elements.