asking advice for Integer Programming packages

Dear everyone,

I don't know much about Integer Programming but am afraid I am facing
a problem that can only be solved via Integer Programming. I was
wondering if those of you who have experience with it could recommend
an R package.
I found the following R packages:

Rglpk
glpk
lpSolve
lpSolveAPI

Are there any others?
Are some of them easier to use than others for a beginner?

Any advice would be greatly appreciated!

Dimitri Liakhovitski
MarketTools, Inc.
Dimitri.Liakhovitski at markettools.com