Based on the discussion on foam grips, I ordered a set of Grip Puppies earlier this week, and they arrived in my mailbox yesterday. I put them on this morning after the ride into work but before really getting started here. This way they can have a full day drying out in the sun before the ride home.
Installation was fairly easy, given three things. (Mostly - follow the instructions that came with them....)
First, test-fit the foam sleeve alongside your grip first, as you may have to trim it a bit. In my case, I needed to remove about 1/3" of foam tube to have a good fit lengthwise. Scissors work well, but go slowly and trim it in several cuts to avoid the "What do you mean it's too short, cut it again!" scenario.

Second, apply soapy water liberally to the inside of the foam sleeve. I found that wetting down the grip itself also helped considerably. You do not need to take off the bar-end weights to get them on, and in fact I would recommend against doing so. Besides that there's no need, the bar-end provides a nice tapered start to get the Grip Puppy over the flare at the outer end of the handgrip.
Third, be patient. You can, in about 2 -3 minutes, get the foam sleeve to slide on; if you force it from the end, it will just bunch up, as it started to on the LHS grip in the picture above. I'll fix that when I have a spare moment later today.
This is a close-up of the end of the grip on the throttle side:

Generally, the Grip Puppies "fill in" the stock grip; the OD is about that of the bar-end weights when installed. To my (ungloved) hand the grip felt secure and about right, size-wise. They feel well-anchored to the handlebars; no slipping is evident when moving the throttle grip.
We have an Indian summer going on here now, so I'm not sure when I will report on how well the heat works through these things; and it will also be interesting to see what will happen when it starts to rain. :-)
But, for around $9 delivered, so far I'm very satisfied.
Good roads,
- Lewellen