Today I actually visited OSGrid! My first try was with my favorite viewer, Firestorm Mesh Beta. I just changed the grid on the startup page from Second Life to OSGrid, and used my OSGrid password.
I got logged in OK, but appeared as an unrezzed cloud to myself. There were other people around, who told me they could see me fine. I tried several "cloud fixes" with no luck, so I logged off, and downloaded the viewer that OSGrid recommends...Imprudence.
This viewer worked great, and my login performance was snappier than I've ever had when logging into Second Life. I arrived in the OSGrid equivalent of an Infohub. There were several other avatars around, chatting. I used some handy signs to grab a freebie avatar, and a list of other landmarks (including some free shopping areas). A nice lady gave me some green eyes and a landmark to her sim.
All in all, it was a very pleasant experience. Gosh, this is a little like when I was just starting Second Life...there is so much to do, I'm not sure what to do first! Work on my avatar? Go shopping? (My inventory consists of a whole 26 items!) Or create my own region?