I can't say much for John Deere but I will mention to you something I encountered recently.
I am in the market for a mower myself, and calling around I spoke with a Hustler dealer. Hustler makes a ZTR, the Raptor, they price at 2999, and Lowes now carries them on a test basis. So I phoned the local dealer / service pro and asked him what they had in stock. He was very fast to say the "We do not carry and will not service any Raptor series mower."
You can draw any conclusion for this you want, but what I see is mainly the fact that Lowes is selling them cheaper then the dealer can, they just don't sell them anymore. The first model available was their Fastrack, a mower who's priced considerably higher than the value priced mowers.
Don't get me wrong, the Hustler Raptor would probably be great for many people, and using your Lowe's card could save you another 5%, but good luck finding someone to work on it with a warranty related repair.
On another note, our local Lowes uses one shop exclusively for their Husqvarna mower repairs. Contacts at that store have admitted they "put Lowes purchased repairs at the back of the line" in most cases.
This is the primary reason I did not choose to shop with the big box stores, and instead, build a good long lasting relationship with a smaller dealer that offers repairs. The hope is that if and when I need service I can get it quick, and be up and running.
Oh and apparently John Deere "dealers" offer to provide you with a loaner lawnmower when yours is out of service. According to several things I've been told just this week. This is something you may want to ask your dealer. Also ask them if they could match or get closer to Lowes price.
Spend a little more, get a little more I say.