I would suggest everyone watch the Klooge tutorial Videos they do give a great overview of some excellent features.
http://www.kloogeinc.com/tutorials.html
KloogeWerks is by far the most feature rich application out there for simulating a tabletop experience via a pc.It is very powerful in what you can do and can really speed up play and automate many teadious things for you,however it does take abit of time to figure it all out.Once you do tho its fantastic.
To really benefit from all those features does take some prep time for your DM but alot of that stuff is a one time thing.
For example Once youve created a Klooge icon for a hill giant you never have to create one again you simple import it into any adventure your using and it will be setup with a graphic token and a full character sheet with abilities attacks ect all there.
As well the community has been creating many player made aids that can be used by anyone.
One such feature we've just started using is the effects feature. Using the downloaded Master effects you can with the click of a mouse applie just about any effect to an npc or player that has a built in duration condition that counts down as your rounds go by in combat.
Klooge is a java based application and its defiantely a strength and weakness.
The benifit is its truly multiplatform so you can use klooge on window,macs,linux ect.
I think the one area that Klooge needs to focus on is where fantasy grounds has it beat..that is spit and polish.You can't deny the fact that Klooge feels like an office app in its interface where as FG looks really pretty and has a much nicer looking interface.
I have an idea on how klooge and address this but i'm not sure if it will be possible.Time will tell.
Oh and yes klooge can support really large jpg maps the users machines is the limiting factor if you want to use maps that are 2500x3500 that expect to need at least 512mb of ram dedicated to the program. If you break up your maps into sections that are 1200x1200 ish you can get away with 256mb dedicated.