I'm a step mom to a 5 year old. We have him every other weekend which works well for us. Being a step mom is constantly a challenge. Half the time I feel like he doesn't care all that much if I'm around or not, but then when he goes back to his mom all he talks about is me! It's totally bizarre! It's been a learning curve for sure, but he's a great kid and we have a lot of fun together (especially now that he's over his "I'm going to have a tantrum for everything" stage when he was 3).
My relationship with his mom has improved a lot, and I think she finally understands that we're all on the same team. Things definitely improved since DH and I got married and I hope the trend continues!
Any other step parents out there? None of my friends are in the same boat and it would be nice to have someone to chat with about this stuff! Especially as we draw closer to TTC!