If you don't do anything to the seams, you will see them after it's painted, even if it's just a little noticable. I had the same delima, and here's what I did. Talked to the guy at Lowes and he said to prime the walls with an oil based primer. If you use a water based primer it could soak through the paper and start to make it peel, so use an oil based primer. Then I added a texture. I used sanded paint from lowes, rolled it on with a mesh paint roller, then used a trowel to knock down the peaks. Afterward, I primed it with latex primer (so that the new/colored paint wouldn't be absorbed by the sanded paint) and then painted. It came out great and wasn't too hard to do. If you don't want to do the sanded paint, you can use joint compound (maybe $10.00 in a huge bucket at Lowes/Home Depot) and hand trowel the wall yourself. You basically just slap joint compound on the walls to create a custom texture. I've done this as well. The key is to NOT go too thick. You don't have to cover ALL fo the wallpaper with joint compound, you just have to make some texture on it. That will cover your seam lines and give you a paintable surface. If you use the joint compound, it's still recommended that you use an oil based primer over the wallpaper so that it doesn't start to pull up where you have the joint compound. Final idea - hire a painter to do it! I had my jack & jill bathroom done for about $400. They supplied all the materials, prepapred & textured the walls, took down the fixtures that needed to be removed, put them back up when done, and painted the walls (I did provide the paint). I thought it was reasonable and well worth the $$ vs. my time to complete (I had already done the kitchen, master bath and 1/2 bath, so I just wanted it done!)
Let me know if you need the name of the painter or any other details on the projects.