I liked my first Avalon so much that I bought another in 2000 and we've put 330,000 miles on the pair. Both are nicked up but they still run fine (2008). In 19 (combined) years of use I've had only ~$3,000 in repairs (other than an accident, tires and oil changes). Cons: Weak in snow. Steerling column leak (both cars - use sealing fluid). Goes through tires too quickly. Toyota's known for quality and reliability and that's exactly what I've experienced. In 2007 I purchased a 1986 Corolla that runs fine. I now need a 4th car and it will be a Toyota. I still feel that I made a solid purchase every time I start up one of my Avalons.
Quality and reliability. Quiet and smooth ride (no noise as others have mentioned). Roomy and comfortable. Good gas mileage.
Variable speed wipers. Improved steering column (leaks). Faux wood trim items on the second Avalon have flaked off.
Few mechanical problems until recently. Within last year replaced rear wheel bearings, engine gasket, & alternator. Marginal paint job as it started peeling from around rear view mirrors at <80K miles. Strut noise has been there from day 1 off the lot (dealer made excuses too). Doors sagged quite early on, but work okay. Door remotes still work (!) although the buttons are about shot.
Wonderful interior room. Very comfy. Huge trunk. Decent gas mileage for its class. Leather seats still look good.
Paint quality. Strut quality. Don't include tan flooring with tan seats (can you say dirt?).
We bought this car used with 34,000 miles on it in 2001, now in 2006 it has 120,000 and shows no signs of wearing out anytime soon. Transmission glides, engine is strong, interior is elegant and comfortable and gas mileage is 31 on the highway. The trunk is huge and the seats feel like your sitting in your favorite chair at home. The only thing I've had done is regular repairs and the air conditioning was charged this year, that's it!