Continental and Bridgestone are both very good companies who both make good products. the OEM tires used on the altima however suck ass. i have experience with the tires in question bcuz my dad has an 07 2.5 S and those tires suck. in an emergency situation where hard braking or quick manuevering may be needed these tires fail miserably. you might be ok for now since u have a lot of tread and u just do cruising but "just for cruising" any tire will do. ive also encountered these tires as they are OE on 02-03 sentra SE-R Spec V's. i bought a set of those wheels for my 2000 altima and they had the factory tires on. (215/45/17 z-rated) they suck. period. hard as rock, unresponsive, loud. they're not alone tho. when i bought my SE-R it had the factory bridgestone potenze S-03 pole positions still on em with a moderate amount of tread left. car only had 15k on the odo. 1 of those pieces of sh!t blew out on me on the highway off ramp. i replaced the 17's w/ BFG G-Force sports. got em for around $100/tire in 215/45/17 which is a great price for that size. excellent tire. the way they outperform the conti's is indescribable. i replaced the bridgestones on my SE-R with Toyo Proxes T1-R's. they are expensive but they are worth every cent that i paid. they cut thru standing water like a hot knife thru butter @ 75 MPH. 1 last thing on this rant. whoever said conti's are OE on BMW's...
BMW OE Tires are Michelin's i knew BMW wouldnt put crap on their cars as OE.
Mercedes Benz OE Tires
Audi OE Tires
1 thing i forgot to mention. BF Goodrich tires are manufactured in michelin plants so u get the same quality/performance in the product but pay less for it. my personal advice to the OP: ditch the conti's and get some michelins or try yokohamas if u dont wanna pay the michelin man.