Kaledor said:
I hadn't considered the use of the badger (being able to tunnel) **VERY** nice trick!
Well, it doesn't do you any good because you won't likely be able to communicate with the badger to tell it to dig anywhere (you need speak with animals or learn celestial and convince your DM that celestial badgers understand celestial). More importantly, however, realize that the badger does not leave behind a tunnel or anything, so the fact that he can dig may not have the uses you think it does.
Jack said:
In specific? A Druid of mine has had fun with Summon Nature's Ally II (Dire Badger) for getting through annoying obsticles - they have a dig speed (only 10 feet, but nothing specifically prevents them from Running for 4 times that in a round, if I recall correctly, for 40 feet of digging per caster level) that is described as being able to penetrate anything short of "solid rock"; you can duplicate the effect with a Celestial Dire Badger via Summon Monster III.
You recall incorrectly. A creature cannot charge or run while
burrowing.
Back on topic, IME summon monster spells are typically very poor. Although you asked for advantages, it's useful to consider the disadvantages.
1. The full round casting time is a real hassle. There's a feat to circumvent this, though, called rapid summoning or some such.
2. The monsters in the spell lists do not progress as fast as the heroes do, so you'll find that by 9th level or so, even your best summoning spells are not that great.
3. A simple 1st-level spell (or spell-like ability, or even Su ability) almost totally negates the summoned monster.
That said, it can be useful, especially at higher levels when the creatures get more abilities and things like protection from alignment don't matter as much. It can also be a lot of fun to buff up your monsters after you summon them. One trick we came up with was a high-level cleric to cast summon monster VII to bring in a huge earth elemental and then buff it with bear's endurance, bull's strength, and spell resistance. The SR allowed it to penetrate protection from evil or magic circle against evil.