From what I've noticed, quite a bit. Basically, the retail version does not come with all of the necessary *.wad files in your cstrike directory. When you buy the Half-Life CD, and then apply the HL updates, and patches, you then can play more maps, which is what most Half-Life servers will run.
Don't fear, I run a Counter-Strike server, and have a download center if you have the retail CD. You can get a patch for the Counter-Strike CD there which has all of the necessary *.wad files and maps that you'll need to play on most servers.
HasteZone Download Center
When you're done, connect to HasteZone

hastezone.uti.com (204.248.52.19:27015)
Hope that helps.