While I can't speak to the Saturn Vue 6-cyl, I did just pick up mine last weekend and we have a 6-cyl Hyundai Veracruz that only has the same towing capacity of 3500 lbs. Had a headwind for most of the way but still cruised along at about 62-63 mph on the flats, and it slowed down to between 55-57 on the hills. This was towing an unloaded 171 that weighed 2478 coming out of the dealer (we weighed it on their scale before leaving) and being just the two of us we don't have much that we will actually be loading it up with when we go camping. Also, when towing I found that it was a very useful piece of advice I had read here about using my manual shifter on the TV to control my rpm's rather than leaving it in automatic mode all the way ... that really was a great piece of advice.
While others may disagree, I think if you have a 3500# towing capacity, plan on getting one of the smaller R-Pods, don't overload it with stuff or drive it with full holding tanks that add a lot of weight that will take you close to your limit, tow it smart and safely, and aren't planning on making 8 hour runs across the Mojave Desert in the middle of summer you should be just fine.