Didn't read all the prior comments so if I am repeating do forgive me. I love the train and have traveled with my family many times. Kids always ask when we can go again. The sleepers are great and if you plan ahead and have flexibility, you can get them affordably (or even free if you have enough Amtrak Guest Rewards points). It's worth getting the Amtrak credit card that comes with 20,000 bonus miles. Starwood points also convert one-to-one to Amtrak points. You can also get Amtrak gift certificates with Amex points.
The sleepers come with all meals for free in dining car. They are considered an upgrade/add-on from your regular fare, but they put you in "1st class" which comes with some minor perks like free water bottles in your room & free coffee or juice available almost all the time in the sleepers, along with the meals. You also get access to the Amtrak lounges -- in Chicago, for instance, the lounge was very recently renovated and you can get free snacks, Peet's espresso from an automated machine, free soft drinks, etc. There was an attendant walking around giving out fancy chocolates last time I was there too...Big hit with the kids.
Pricing for sleepers is very confusing. Basically the earlier you buy, the cheaper they are -- but if you wait until the very last minute (like the same day) you can sometimes also get them for cheap -- I recommend calling as well as looking at website. Also I have read that they do not do the onboard upgrades anymore except at full price. Amtrak also uses a bucket system, so some rooms on the same train will be more expensive (or less expensive) depending on how things are selling. They can be VERY expensive...or not.
The cars are mostly old and show it. Sometimes temps in the sleepers are too high, sometimes too cold. Plan accordingly. I just read someone recommending that you bring duct tape to secure loose banging things in your sleeper for better rest, which is a good idea (sometimes stuff like the little closet door or the bathroom door can be loose, etc.) A white noise machine or earplugs can be good too -- we were close to the engine once which blew the whistle at every single crossing across Ohio in the middle of the night, which seemed like about 1,000 crossings and I was woken up many times. The wine available on board is not bad at all -- buy it in the cafe car, it might help you sleep.
Amtrak.com does not allow you to search for a range of dates to see which might have the cheapest sleeper fare. Thankfully someone actually sat down and made an app for this, which is at
http://biketrain.net/amsnag/amSnag.php .
If you are not in a hurry and can be laid back about most things like the above loose doors, I really do recommend the train. 95% of my experiences have been great. (Amtrak sometimes runs late...very late. They share the tracks with freight trains, among other things, and that can screw everything up. However most of my trips have been pretty close to on time, even on the Lakeshore Limited, whose nickname is the "Late For Sure Limited.") Tip the sleeper car attendants. It's a really interesting way to see the U.S.
I dream of the day that we actually have something resembling a decent cross-country rail system again. I really hope it happens before I'm old. It is so nice to arrive somewhere feeling totally chill instead of miserable after being smashed like sardines into a metal tube.