starline: Here is my experience of using some of the clients mentioned. I am using a 200 mhz pc with 99 mb of ram and a 15 inch monitor (this PC is old!):
'PANDA - gGo' - Java program. I used this when it was just called gGo. Then it was unbearably slow and pretty much unuseable, although that may have changed with later releases.
'Jago' - this is great! The best client I have found. Connects to IGS and some other servers. Easy to use. Good SGF editor. Plays gnugo. Jago has some nice features and is amazingly fast for a java program.
'Panda Egg' - for connecting to IGS. Simple interface (although the board/chat combination is abit awkward on a 15 inch monitor) and easy to use, especially for a beginner. Lacks features, especially missing is the ability to save games as SGF, however you can save/replay games using its own 'UGF' format.
Funkybside: For those not using a P1 200 MHz w/ 99Mb ram, IMHO Panda-gGo is a very nice client. I enjoy it for IGS better than any other client I've tried. Very good GUI, and the 'styles' are a neat feature. The system used to display players/games/chats is very efficient and great for those of us with larger moniters and highter resolutions. The look of the goban and stones is good as well.